Math Whiz Breaks Calculation Record

keyshawn632 writes "The Associated Press reports that Gert Mittring, 38, needed only 11.8 seconds to calculate the 13th root of a 100-digit number in his head at a math museum in Giessen, a small town, located in western Germany. It's worth noting though that his feat will not be recognized by The Guinness Book Of World Records because of the difficulty of standardizing such mathematical challenges."

Comments

Hrmm

[TheKidWho]

Probally had some special algorithm developed specifically for that purpose. And what is the practical purpose of this? Other then he wasted a good deal of time figuring out how to find the 13th root of a 100 digit number in his head?

Re:Hrmm

[AnimeKid]

Probably just a feat that is well regarded but doesn't serve much other than the "oooooo" factor? Just my guess.

Re:Hrmm

[Travy.b]

11 odd seconds aint a great deal of time mate ;)

Re:Hrmm

[DEBEDb]

How long did it take to write this post?

Re:Hrmm

[Anonymous Coward]

It would take me more than 12 seconds just to read a 100 digit number.

What?

[HardJeans]

I can't even read 100 digits in 30 seconds.

Re:What?

[ricotest]

The dude can memorize a 22 digit number in four seconds (according to the article) so I'm sure he can take a similar time to juggle the numbers around in his head. Perhaps his mental algorithm focuses on certain numbers at a time so that he can handle it.

Re:What?

[Anonymous Coward]

...so I'm sure he can take a similar time to juggle the numbers around in his head.

Pfft, They just make it up...

Re:What?

[jsprat]

Here is a list of two other records he holds. It hasn't been updated for the one mentioned in the myway article.

Notice it took him 44.7 seconds to calculate the square root of a six digit number, but only 11.8 seconds to calculate the 13th root of a 100 digit number!!!!

He also calculated the 23rd root of a 200 digit number in 40.83 seconds.

Re:What?

[hackstraw]

Let me try some rough math with the help of a calculator.

To memorize 22 digits, this guy takes ~4 seconds. So for 100 digits that would take about 18 seconds.

Now I forgot, he did what in 11.8 seconds

Re:What?

[johkir]

How long did it take to recite the answer?!?!

Re:What?

[iamhassi]

remind me to not let him see my credit card...

Re:What?

[MntlChaos]

not too long, 13th root of 10^100 is about 10^100/13 or about 10^8, so we have a number under a billion

Re:What?

[MacDork]

22 digits... It's all a matter of how you look at the numbers. For instance,

1492313371983

Is much easier to memorize as

1492, 31337, 1983 right?

22 digits is really just 3 phone numbers plus a digit. So with all the brain power out there reading Slashdot, you geeks mean to tell me if three knock dead gorgeous babes gave you their... oh.. Slashdot.... nevermind ;-)

Re:What?

[Anonymous Coward]

But he didn't have to memorize the 100-digit number, did he? It took him 4 seconds to memorize 22-digit number, but probably took him a second to read it through. So instead of wasting time memorizing it, he just produced the result. I can see how that could take him 11.8 seconds instead of >18 seconds

Re:What?

[Titanium Angel]

According to this, he can also calculate the 23rd root of a 200 digit number in 41 seconds. There's also a picture of him there.

Re:What?

[the angry liberal]

Dude, chicks are so turned off by guys who will be able to remember phone numbers like that.

Having such a memory leads to other problems:

a) She will expect you to remember her birthday/holidays

b) She will know you will remember all the dumb things she said the last time you got in a fight

c) She will know you are smart enough to balance the checkbook (less money for her!)

My advice: Play dumb. It turns them on for some reason.

Re:What?

[Hobadee]

...musta cheated... he must just memorize his 13th power tables!

(Oooh! I recognize that number! It's blah^13!!!!)

Re:What?

[mwvdlee]

I couldn't even write down all the digits in the answer in 11.8 seconds!

Re:What?

[theboyhope]

Nice shirt, for a boat person.

Re:What?

[ricotest]

Now I forgot, he did what in 11.8 seconds

Clearly, your memory abilities aren't quite as good as Mittring's :)

Re:What?

[henrygb]

The square root involves the first five places after the decimal point of an irrational number, while the thirteenth root results in an integer - this allows some tricks.

Show me any 13th power of an integer and I can immediately tell you the final digit of the root. Similarly with 5th powers and 9th powers. But square roots of non squares don't give so many tricks.

Re:What?

[op00to]

Why don't people teach this in schools? Obviously this kind of stuff is pretty tricky, but there must be other interesting little tricks and relationships that when taught correctly, could have interested a whole lot more kids in math. Where'd you learn this?

Re:What?

[Crayon Kid]

Yeah, you wouldn't want him to extract the 23rd root from the number.

Re:What?

[drDugan]

Why don't people teach this in schools?

what is taugh in US public schools is mostly just politicized conformity -- designed to produce older children that have ... oh wait, it's not designed at all. it's pretty much all crap. and intelligent design. even in private schools and grad schools, no one ever is taught to really think for themselves as a part of the curriculum. physics is the closest. but to really think for yourself, you have to find your own teachers and they are not in "schools"

all the real learning I did after I left school, after I got 7 letters after my name... what a waste.

Re:What?

[Phisbut]

How long did it take to recite the answer?!?!

From this article:

The Rules
...
4. The timing begins when the number becomes visible to the competitor and ends at the end of writing the answer.
...

so the 11.8 seconds include both the mental computing and the writing down of the answer...

Re:What?

[garaged]

Been there, done that !!

Actually :-)

I dont have this guy's memory and math capacity, but I can remember some things others forget, it is kind of a problem, because I get to "analize" conversations from a day ago, and find lies and conections with other conversations or even attitudes people have.

It's good for me because i can actually know if someone lied to me, but its anoying for the significant other cause sooner or latter i will find out if she lied to me :-)

Re:What?

[RichardX]

Look up trachtenberg speed math - it's a system of (cheats/optimizations) depending on your point of view, for doing mental math.. either way it lets you get a correct answer very quickly, so it's useful.

Re:What?

[RichardX]

I just found a good little example of some of the concepts in the trachtenberg system here

Re:What?

[jproffer]

I'm not sure you can calculate a number in your head without first memorizing it? Probably they are just calculating the actual calculation time, not the time it takes to read the number (since its not part of one's computational abilities, anyway)

Re:What?

[Com2Kid]

• oh wait, it's not designed at all. it's pretty much all crap. and intelligent design. even in private schools and grad schools, no one ever is taught to really think for themselves as a part of the curriculum.

You know I used to half way believe this, until I got some friends who came over from the Asian schooling system.

Americans are INCREDIBLE at taking story problems and real life scenarios and doing mathematical modeling on them.

Heck just yesterday I saw a Seasame Street game that was basically an introduction to Venn diagrams! That is at the pre-school level, once you actually get into the schooling system, well, here are just a FEW of the things American school children know about that seem common place to us, but are complete mysteries to others!

• The planets, names, sizes, that they even EXIST.
  
• Atoms, molecules, etc.
  
• Anything dealing with biology.
  

(Please note, this list may not be applicable in the southern states.)

The American Educational System needs an overhaul, for sure, our basic mathematical and linguistic education bites, but when it comes to finding creative, or just worldly, solutions to problems, well, we at least have that covered fairly well.

Re:What?

[md65536]

What is the square root of 1,522,756?

You only need to know the first digit (and its place of course) to calculate the first digit of the square root (more than 1M but less than 4M so the root is between 1000 and 2000). You can start calculating immediately without even reading the other digits.

I use sqrt as an example because I don't understand 13th roots so intuitively, however someone else mentioned that there are a lot more tricks with 13th roots than there are with sqrt.

Also note, 1234*1234 = 1,522,756 and 1235*1235 = 1525225... a difference of 1 in the root is a difference of thousands in the square, so if you know it's an integer you don't ever have to bother with more than the first 4 digits.
A 100-digit number will have a 13th root somewhere around 50,000,000. I don't know any tricks or algorithms he might use, but I'd be willing to bet he doesn't have to memorize more than 8 digits.

For example
50,000,000^13 = 1.220703125e+100
50,000,001^13 = 1.2207034423828505859402929688896e+100 ... which are different on the 8th digit. Knowing more digits than 8 doesn't matter because there are only non-integer roots between those 2 numbers.

I can do better

[Attar81]

I can say all fifty states in a quarter of a second!

Re:I can do better

[comwiz56]

Lois: Peter, why would they make you presidesnt?
Peter: Maybe it's because I can recite all 50 states in a quarter of a second - RARF!
Lois: Peter, that was just a loud yelping noise

Re:I can do better

[NanoGator]

"Name a state. Within a second, I'll tell you the capital of it."

"Wisconsin"

"W."

Re:I can do better

[smittyoneeach]

Oh, yeah? Well, I actually went to Giessen, Germany, once, to visit someone.
I can confidently report that it is a Pödünk.
My wife reports that Giessen sports its own license plate code, to which I say: it's still a Pödünk.

Re:I can do better

[Anonymous Coward]

I can say all fifty states in a quarter of a second!

OK, I'll try it.

<timer status=on>"All fifty states."</timer>

OK, that took 60/100 second.

That's nothing

[bmzf]

I can do that with my eyes closed. It'll just take me a bit longer.

Re:That's nothing

[TheLink]

Well, I can do that with one hand tied behind my back. I'd need the other hand free to do the calculation though.

And a PC.

Re:That's nothing

[Anonymous Coward]

hell i can do it with my eyes tied behind my back

Re:That's nothing

[Anonymous Coward]

hey that was supposed to be my line, you jerk

13 is an unlucky number!!!!!

[Anonymous Coward]

Now what if a black cat crossed his path!!!!! He would then like factor the matrix code and the world would hang in an infinite loop from the resulting glitch!!!!!111

OMG OMG OMG

"memorizing 22 random digits in just four seconds"

[AnimeKid]

"memorizing 22 random digits in just four seconds" (per the article) God... Wonder if they were 22 individual digits or one huge number. If it was the former...wonder if the ordering was relevant... Hell I have a hard time remembering phone numbers beyond my own =\ I'd like his brain >=D

That's easy.

[rackhamh]

Just memorize the 13th root of every 100-digit number in existence. Sheesh.

Re:That's easy.

[Highpriest]

It would all depend on how many floating point digits he had to calculate. Continuing digit division on a floating point number isn't hard if you only have to calculate 5 places. But if the significant digits were say 20 and it had to be done in 11 or so seconds that would be an extremely hard feat.

Re:That's easy.

[wildsurf]

Just memorize the 13th root of every 100-digit number in existence. Sheesh.

Let's just think about this for a minute.

100-digit numbers will fall between 10^99 and 10^100. Thirteenth-roots of such numbers will lie between 10^(99 / 13) and 10^(100 / 13), or in the range [41246264 .. 49238826]. That's about 8 million possibilities, and the distribution is far from linear.

But it's linear enough that the first nine digits of the 100-digit number yield a unique possibility for a root. And the last digit of the root will be the same as the last digit of the 100-digit number, because (N mod 10) always equals (N^13 mod 10). So the problem can be tackled from both ends, with the middle digits of the root being the hardest.

Of course, if the audience members are clued in, they can still beat the mental calculator hands down. Type the first nine digits, take the thirteenth root, and start reading off the digits; round up slightly to make the eighth significant digit match the final digit of the 100-digit number. Done.

A college professor of mine taught us how to square 3-digit numbers in our head in seconds using tricks like this; he was able to multiply arbitrary 5-digit numbers in his head, and often performed this onstage. And for the curious, yes, I do actually have a life outside slashdot. :-)

Re:That's easy.

[Eric_Cartman_South_P]

Just memorize the 13th root of every 100-digit number in existence . Sheesh.

Thanks for mentioning that, imagine the time I would have wasted had I tried to memorize all the 100-digit numbers that DONT'T exist. Thank you!

Re:That's easy.

[Anonymous Coward]

if you're going to mention Professor Benjamin you mind as well use his name :)

Re:That's easy.

[wildsurf]

if you're going to mention Professor Benjamin you mind as well use his name :)

You beat me to it. (Retroactively.) Sorry Art. :-)

P.S. Try solving one of these in eleven seconds. :-)

Re:That's easy.

[Old Wolf]

The article didn't say whether the number had an integral 13th root or not (While reading it, I was thinking he would give the result to 3d.p., or something, which seems like quite an amazing feat to do in 11.8 seconds).

It would be a better challenge if the computer came up with a random base (3 - 30, say), and a fairly random large number (that had an integral root in that base), and then they timed the guy over say 10 of these challenges.

Re:That's easy.

[vyrus128]

> A college professor of mine taught us how to > square 3-digit numbers in our head in seconds > using tricks like this; he was able to multiply > arbitrary 5-digit numbers in his head, and often > performed this onstage. And for the curious, yes, > I do actually have a life outside slashdot. :-) Did you happen to go to Harvey Mudd College?

Re:That's easy.

[n3k5]

Just memorize the 13th root of every 100-digit number in existence.

Boy, you're such an overachiever. Unfortunately, the article doesn't say, but as the result was recited in a matter of seconds, I think it's save to assume that it had to be an integer number. So you'd just have to memorise the 13th power of every integer for which it is 100 digits long. This reduces the number of possible tuples down to less than ten million -- eeeeasy!

Re:That's easy.

[Anonymous Coward]

My cat's breath smells like catfood

Re:That's easy.

[Anonymous Coward]

This is easy. As long as the 100-digit number is 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000001 .

Re:That's easy.

[citog]

As one spelling nazi to another; it's "don't" or "DON'T" if you prefer the noise.

Re:That's easy.

[Rufus88]

because (N mod 10) always equals (N^13 mod 10)

I know I'm going to kick myself for asking this, but why is this necessarily true?

Re:That's easy.

[thatnerdguy]

what about imaginary numbers? do those exist?

Re:That's easy.

[stoborrobots]

it isn't always - it's only true for numbers which are not even and not multiples of 5...

As for why it's true otherwise, it's because of Fermat's Little Theorem and Euler's Totient Function...

Specifically, since the Totient of 10 is 4, any number which is coprime to 10 (i.e. not even and not a multiple of 5) when raised to a power of 4, yields a 1 in the units place, (i.e. N^4 = 1 mod 10 if gcd(N,10) = 1).

Since if a number is coprime to 10, then all its powers are coprime to 10, N^12 = (N^3)^4 also has a 1 in its units place.

Now N^13 = N*(N^12) will always have the same last digit as N, if N is coprime to 10.

Re:That's easy.

[kylemonger]

(n mod 10) = (n^k mod 10) iff (k mod 4) = 1. (n > 0, k > 0)

Since we use base 10 arithmetic (n mod 10) means we just look at the last digit. Digits repeat every fourth iteration when computing the powers of a natural number.

Numbers ending with:
1 -> 1,1,1,1,1,1,1,1,1,...
2 -> 2,4,8,6,2,4,8,6,2,...
3 -> 3,9,7,1,3,9,7,1,3,...
5 -> 5,5,5,5,5,5,5,5,5,...

You can see the period 4 cycles for 4, 6, 7, 8, and 9 as well. Since the digits repeat, the value of (n^k mod 10) must also repeat as k increases.

Re:That's easy.

[wildsurf]

Did you happen to go to Harvey Mudd College?

Why yes, class of '94. And of course, the professor is Art Benjamin. Did you go there too?

Re:That's easy.

[rhuntley12]

Dude, what?

Re:That's easy.

[k98sven]

it isn't always - it's only true for numbers which are not even and not multiples of 5...

What?

4 is even. 4 mod 10 = 4
4^13 = 67108864, 67108864 mod 10 = 4

5 is a multiple of 5.
5^13 = 1220703125, 1220703125 mod 10 = 5
5 mod 10 = 5

Re:That's easy.

[stoborrobots]

I guess what I meant is that the proof (or at least, the only one I can remember) is for the case of numbers which are coprime to 10...

See the other reply below about how it's also true for those cases... But for some reason I can't quite get my brain to cough up the proof for the general case... (Which is disappointing, time to turn in my Maths degree...) I can feel the slightest hint of a proof in the back, a gut feeling that it's right, but all that comes out is the routine proof as I studied it in Discrete Maths...

http://www.gallup.unm.edu/~smarandache/euler-gn.tx t seems like it might help... If my mind wakes up and helps, I might post the general solution later...

Re:That's easy.

[Anonymous Coward]

(n mod 10) = (n^k mod 10) iff (k mod 4) = 1. (n > 0, k > 0)

"iff", usually short for "if and only if", is definitely not true as claimed above. Take for example, n=1 and k an aribtrary natural number, or n=4 and k=3 [n^k = 4^3 = 64 but (3 mod 4) = 3].
So, Euler's Theorem [http://en.wikipedia.org/wiki/Euler's_theorem], of which the parent's statement is a special case, is a proper implication and not an equivalence.

As an afterthought..."iff" was maybe just a typo.

Although

[Striker770S]

with the amount of high calculating that he does know, it would probably throw him off if they ask what 1+1 is =p

Re:Although

[BladeMelbourne]

I know that one!

1 + 1 = 10

Re:Although

[Anonymous Coward]

nah, my security professor told me 1 + 1 = 0

Re:Although

[TheRaven64]

Nah, 1 + 1 = 11, in at least two encodings I can think of. I'll give you a while to think about it before I post them...

Re:Although

[Rubyflame]

Okay. 1+1=11 in unary.

And with overloaded operators, you can add two strings, so "1"+"1"="11".

Re:Although

[TheRaven64]

Yes to the first one. The second, while technically correct, is not what I was thinking about (I was restricting myself to numerical values).

My second encoding was a grey code. A grey code is one in which only a single digit changes when a value is incremented by one. They are particularly useful on mechanical computational devices. One of the most common ones works as follows:

1 = 1
2 = 11
3 = 10
4 = 110
5 = 111
6 = 101
7 = 100
8 = 1100
9 = 1101
10 = 1111

Unlike binary, where each column is multiplied by 2^(n-1), or decimal, where each column is multiplied by 10^(n-1), the columns in this code represent (2^n)-1 (where n is the index of the column from the right, counting the units as 1). To complicate matters further, the sign of each column alternates for non-zero columns, with the first non-zero column from the left being positive. 1101 can therefore be worked out as:

((2^4)-1) - ((2^3)-1) + ((2^1)-1)
= (16-1) - (8-1) + (2-1)
= 15 - 7 + 1
= 9

It is worth noting that once you pass 4 bits, there are multiple possible grey codes.

I can (seriously) do 43rd root of 100 digit number

[Anonymous Coward]

Record? How do you know it was a record? Probably he himself claimed it was a record and the press published it.

When I was in college, I received some training from a genius about how to do these calculations. I practiced and could calculate 43rd root of a 100 digit number 1 to 3 seconds. Is that a better record? I am sure there are literally hundreds of people who can do this.

Break RECORD?

[Anonymous Coward]

How could he break a record if there is no proper documentation on such feats?

Family guy

[comwiz56]

Obligitory Family Guy quote:

Lois: Peter, why would they make you presidesnt?
Peter: Maybe it's because I can recite all 50 states in a quarter of a second - RARF!
Lois: Peter, that was just a loud yelping noise

Re:Family guy

[Anonymous Coward]

Please, that is *so* not redundant.

Now, this comment, this is redundant.

Wallow in redundancy!

Sources report...

[Anonymous Coward]

...Mittring will now go for the record of longest lifespan without losing one's virginity.

Re:Sources report...

[mollymoo]

Mittring will now go for the record of longest lifespan without losing one's virginity.

RTFA

It says he's already got the 13th root, that's 12 more than required!

Re:Sources report...

[Anonymous Coward]

I'm afraid he has some stiff competition here ;)

(no pun intended)

Re:Sources report...

[Anonymous Coward]

Whatever, I would do him!

Re:I can (seriously) do 43rd root of 100 digit num

[Anonymous Coward]

no no no, it's because it's http://apnews.myway.com//article/20041124/D86IDI10 0.html Gert Mittring, 38. That is why it is a record ;)

Re:I can (seriously) do 43rd root of 100 digit num

[AnimeKid]

"Onlookers with electronic calculators needed more time to solve the problem that Gert Mittring figured on his own, with two umpires checking the time, at a math museum in the small German town of Giessen near Frankfurt in western Germany." Per the article.

And the answer is:

[fred911]

Five. Everyone knows that!

Re:And the answer is:

[goon america]

you misspelled "forty-two".

Re:And the answer is:

[Anonymous Coward]

That's three, sir.

Re:And the answer is:

[Anonymous Coward]

actually it is "forty two"

Re:And the answer is:

[Anonymous Coward]

actually it is "stfu"

Wow..

[Maxite]

Something not even I can do, even if I tried.. But I wouldn't even want to do that. Cheers to the fellow.

Re:Wow..

[Anonymous Coward]

you mean with a calculator?

Sweet

[Anonymous Coward]

Sweet

Really?

[zealousness]

Can he really calculate the 13-th root of any given 100-digit number mentally in 12 seconds? If true, that's too amazing....

I can hardly believe that. Just imagine how long he takes to memorize the 100-digit number...put it into his head, then do the calculation...-.-

just wondering...

Re:Really?

[izomiac]

I doubt that he can do it for any number, other wise that would make 128 bit RSA encryption useless. I'm guessing that he did something like figure out if it's divisible by 2 (look at the last digit), then 3, then 4, 5, 6, 7, 8, 9, 10, and so on until he got to the thirteenth number that it was divisible by. Too bad they didn't pick a prime number and let everyone stand there mentally dividing.

Re:Really?

[damiam]

Roots != factors. Finding a 13th root has nothing to do with RSA; a calculator can do it in a couple seconds.

Re:Really?

[izomiac]

Oops, guess I read it wrong. Wow, calculating roots is impressive.

Re:Really?

[CProgrammer98]

huh? roots != factors?

so, 2 * 2 * 2 = 8... is the 2 a root or a factor? It's both.

What you should have said was roots are special case factors.

Re:Really?

[damiam]

Not necessarily. The cube root of 42 is ~3.476, but that's not a factor of 42. There's occasionally overlap between roots and factors, but they're different (though related) concepts.

Re:Really?

[CProgrammer98]

true, (there's also the imaginary roots of course) I was assuming that the challenge only involved integer roots... I didn't make that clear in my comment

38, ohhh

[photon_chac]

According to Neumann's thoery, a math guy reaches his peak at about 26, could this _Gert Mittring_ be a bit more 'number-crunching' at that age?

Re:38, ohhh

[Anonymous Coward]

You have to wonder how much of it is actual math skill versus computational skill. I think the 26 year figure was for a mathematician, which I take to mean someone who does mostly theoretical/abstract proof work. I have professors who are quite good at what they do, some with books and numerous papers written, who can't calculate simple arithmetic in their head. The two aren't necessarily connected. Being that I've never heard of this guy before and have done a decent amount of reading on modern mathematics, I wouldn't be entirely surprised that this is just a "freak" ability and not an indication of a "math whiz."

Re:38, ohhh

[Anonymous Coward]

Why 26?

Why 26? I know thats how old Einstein was when his first four famous papers came out.

Anyone else? I'd like to read up on Neumann's theory about this. Always interested in that sort of thing like after 30 being hopeless for most scientist and mathematicians.

Re:38, ohhh

[iannn]

because after 30 you may not have as much drive to push yourself, especially if you've already made it. also, you have teaching duties, a family, etc.

it's easier to work 10 hours a day if you're a graduate student.

and there have been plenty of ground breaking achievements by people over 30, just look at archimedes, gauss and poincare, to name 3.

Re:38, ohhh

[Anonymous Coward]

So its mostly superficial?

To say that the mind is slower after a certain point is obviously true, but not to the point it would have any detriment to long-term in depth thinking like the sciences and math when you ponder?

I mean, things like quick arithmetic will take a little longer, but the thought process and so forth for deeply understanding a topic will still be around, right?

heh

[NeoGeo64]

This reminds me of that movie Rainman where he could do complex calculations in his head. He also read phonebooks for fun.

11.8 Seconds

[dupper]

Definitely 11.8 seconds.

Yes, But...

[Anonymous Coward]

Does he run Linux?

Re:Yes, But...

[mrchaotica]

No, he runs Windows. If he ran Linux the calculation wouldn't have taken so long. : D

Re:Yes, But...

[hunterx11]

I wouldn't necessarily trust a Windows calculator.

Re:Yes, But...

[goon america]

He would just have to spend a few hours mucking around in the configuration files

Re:Yes, But...

[mrchaotica]

Heh, good point! Now that I think about it, he might need to spend some time compiling all his software, too...

How to Play the Flute

[Anonymous Coward]

I smell Monty Python .

Re:So Guinness not suck now?

[b0lt]

Er, wrong Guinness. The one mentioned in the article is the world record Guiness. The one you linked to is the beer company.

Ironic...I'm currently listening to...

[taradfong]

Just as I read this article, what would start playing in my playlist but Mr. Roboto. I wonder if he has parts made in Japan?

Re:Ironic...I'm currently listening to...

[KJKJava]

rofl. machines dehumanize! great song.

Solution using Parrot/Perl6

[Anonymous Coward]

Perl6/Parrot lets you solve this problem using far fewer lines of code. Take a look.

I think I saw that guy...

[NotQuiteReal]

... lurking near the ATM, looking over my shoulder, memorizing my PIN.

Re:I think I saw that guy...

[dousk]

..... and he could probably stand there and look at 25 - 1 more guys' PIN before he had to start writing down :-D

Re:I think I saw that guy...

[Anonymous Coward]

If he can memorize a 100 digit number and then calculate the 13-th digit, then he can probably read our minds anyway.

Or wave his hand infront of you and make you give him your PIN number. "You want to give me your PIN."

Re:I think I saw that guy...

[Class Act Dynamo]

Yes, but the fact that he has this talent percludes him from being able to take the actual ATM card away from even an able-bodied middle-schooler.

And still has 0.00005% of getting laid

[gelfling]

did he figure that one out?

Re:And still has 0.00005% of getting laid

[xeyr]

As opposed to your average sleek, athletic slashdotter who is a regular sex machine.

Re:And still has 0.00005% of getting laid

[fireman sam]

I think a better joke would be.

And that would be the only rooting this guy will ever do in his life

Re:And still has 0.00005% of getting laid

[Poppageorgio]

That smart, and holding 3 degrees, I'm sure this guy has plenty of bucks. If you've got money, you can have a hot girlfriend. Looks and money are on a linked scale. Good looks + no money = Laid. Ugly + $$$ = Laid. Net effect is still the same.

11.8 seconds?

[eeg3]

Ha! I can calculate that in a mere 3.14 seconds, infidel!

Re:11.8 seconds?

[tominfinitenerd.com]

yum, thanksgiving pi

Re:11.8 seconds?

[jacksonj04]

It takes me about 30 seconds to build an expression on my palmtop which allows me to find the nth root of any number. Does this get me bonus points for not only taking very little time, but also for saving me potentially a whole minute in my future life where I may have to perform this calculation?

God bless technology.

And it's 3.141592653 seconds (from memory)

Re:11.8 seconds?

[damiam]

30 seconds? The expression is x^(1/n). Why does that take so long?

Re:11.8 seconds?

[An ominous Cow art]

I and 2 of my friends memorized pi to 50 places in high school, on a bet. I can still recite it today, over 20 years later.

Re:11.8 seconds?

[CableModemSniper]

grafatti gets confused by parens?

Re:11.8 seconds?

[Anonymous Coward]

So you lost?

Re:11.8 seconds?

[jacksonj04]

That exact reason in fact :D

Re:11.8 seconds?

[jacksonj04]

User friendliness.

This is very nearly as important

[Anonymous Coward]

...as the ability to break 2x4's with your bare hands.

Re:This is very nearly as important

[CrankyFool]

Unfortunately, he _still_ can't pound a 6" spike into a 2x4 with his penis. And everyone knows, a girl's got to have her standards.

Re:This is very nearly as important

[OneOver137]

I watched that movie last night! Kent! Kent! This is Jesus...

Re:This is very nearly as important

[Anonymous Coward]

...errr, if he could do that, why would he wasting his time with 100 digit numbers?

Cooling

[Anonymous Coward]

Did they say what type of cooling unit he used to avoid brain meltdown? He's gotta be way overclocked.

record

[Coneasfast]

He does hold the world record for memorizing 22 random digits in just four seconds

another incredible feat! that's impressive, this guy is a superhuman. seriously, it would take me a good 15 minutes (maybe more) to memorize 22 random digits.

Re:So Guinness not suck now?

[BJH]

They're the same company, dipstick.

Re:I can (seriously) do 43rd root of 100 digit num

[imsabbel]

You know what. Back, in my jedi-training, i was SOOOO strong in the force i could let the sun shine out of my ass!
Dont believe me?
I dont believe you either.
So stop bullshitting.

Bounds

[Shishberg]

Can someone confirm this maths... it seems that the 13th root of a hundred-digit number must be between 41246264 and 49238826 - a range of about 8 million. So it's actually narrowed down for him.

A bit.

By some definition of "narrowed down".

Okay, he's still a freak.

Re:Bounds

[Anonymous Coward]

I can confirm that there is no such word as 'maths' you smelly limey freak.

Re:Bounds

[Atealtha]

maybe he just memorized 13th root of all 3 digit numbers? The range is now 899, sort of.

Someone already mentioned his memorization skills. I think this was the trick. Someone memorized tons and tons of digits of pi. So when someone starts reading a random section of digits he can recite the next hundred or so. Doesn't mean he calculates pi every time.

Re:Bounds

[Anonymous Coward]

Actually, the bounds are 49,238,826 to 58,780,160, a range of 9,541,334.

Re:Bounds

[Anonymous Coward]

100 digit number, not a number: 99 < x < 1,000

Re:wow

[Anonymous Coward]

Most people can drink a beer that fast, and, of course, I assume you mean a pint of beer, not a bottle....

Guiness Book of World Records sucks anyhow...

[TWX]

For all of the real records of achievement that exist in this world, there are numerous examples in their book of utter crap that doesn't amount to anything. The most people in a pie eating contest in one place. The most times running through a field serviced by multiple beehives. The largest cheese sandwich. The Houston 500. Etc, etc, etc.

Re:Guiness Book of World Records sucks anyhow...

[Anonymous Coward]

It's bound to be crap. It's there to settle bar bets. I hope they don't waste money making quality products for drinkers.

Re:Guiness Book of World Records sucks anyhow...

[Johan Veenstra]

You do know what Guiness is, right?

Re:Guiness Book of World Records sucks anyhow...

[nacturation]

And they leave out the really interesting world records, such as the largest breasts in the world. Wouldn't that be of more interest than the average schlock they publish?

Devi: another brilliant mathematical mind

[GreenPenInc]

When I was a kid, my dad lent me a book of Shakuntala Devi's book, "Figuring". She was famous some years ago (in the 50s, I believe) for her own computational ability, multiplying two 13-digit numbers in her head in 28 seconds.

The book itself was an interesting read, and at the time I just ate it up. It has a lot of tricks regarding number theory, mathematical riddles, calendar tricks, and calculation of pi, for example. It teaches how to figure the day of the week for any Gregorian date of any time in a few seconds, a trick which I still remember and use today!

As for the Pi, it contained a few poems and sayings whose letter counts signified the individual digits. I started trying to memorize pi, with my sights set firmly on the world record (as I am not without my own mathematical and mnemonic prowess). However, around grade 9, I decided to abandon my quest in order to get a life. I had memorized 1350 digits at that point.

One such quote held little significance for me at the time, but has since become hilarious. "How I want a drink, alcoholic of course, after the heavy chapters involving quantum mechanics!" Needless to say, my quantum prof found it quite funny. :)

Re:Devi: another brilliant mathematical mind

[corbettw]

However, around grade 9, I decided to abandon my quest in order to get a life. I had memorized 1350 digits at that point.

Damn, you were too late.

Re:Devi: another brilliant mathematical mind

[JohnFluxx]

"It teaches how to figure the day of the week for any Gregorian date of any time in a few seconds, a trick which I still remember and use today!"

Me too. Although I always forget what doomsday is this year (Sunday iirc).

Re:Devi: another brilliant mathematical mind

[Skeezix]

I'm not sure which method you use, but I included one method in an article I wrote on memory improvement which some slashdot readers might find interesting.

With some practice, you really can get to the point where you can calculate days of the week for any date in just a few seconds. People don't realize it's not all that difficult so it's a nice parlor trick.

Also included in that article are methods for remembering long-digit numbers, the order of a deck of cards, etc.

Re:Devi: another brilliant mathematical mind

[Anonymous Coward]

some similar books were writen by a russian guy named Trachtenberg while he was in a german death camp durring ww2. Interesting stuff.

Re:Devi: another brilliant mathematical mind

[rlanctot]

The formula is called Zeller's Congruence. I wish I'd known it existed before deriving it by hand for my programming class =\.

Re:Devi: another brilliant mathematical mind

[DroopyStonx]

It teaches how to figure the day of the week for any Gregorian date of any time in a few seconds, a trick which I still remember and use today!

Care to share? Sounds interesting!

Re:Devi: another brilliant mathematical mind

[eihab]

A quick googling led me to this page which looks like a decent way to go about doing it.

Re:Devi: another brilliant mathematical mind

[ilyanep]

With no tricks I managed to memorize 3.14159265358979323 (my friend has about 5-10 more digits memorized). Needless to say, I have no life.

Re:Devi: another brilliant mathematical mind

[glamslam]

http://mathforum.org/dr.math/faq/faq.calendar.html /

Re:Devi: another brilliant mathematical mind

[Anonymous Coward]

Man, I can't, I shan't, formulate an anthem where the words comprise mnemonics, dreaded mnemonics for pi.

#52

Re:Devi: another brilliant mathematical mind

[ezzzD55J]

As for the Pi, it contained a few poems and sayings whose letter counts signified the individual digits.

Sir, I have a rhyme excelling
In mystic force and magic spelling
Celestial sprites elucidate
All my own striving can't relate

:)

Re:Devi: another brilliant mathematical mind

[thetroll123]

Oh wow! My dad gave me the same book, haven't thought about it for years. I remember the story about putting a grain of sand on the first square of a chessboard, two on the next, four on the next etc. I spent the rest of the day calculating 2^63 with a pen and paper. Think it started with a 9 :-)

There was also one about a lily pad which doubled in size every day to completely cover a pond from the first to the last day of June... So what date did it cover half the pond? Yup, I guessed the 15th...

Thanks, dude, happy memories!

Re:Devi: another brilliant mathematical mind

[Anonymous Coward]

Why not memorize something useful? Man, what a waste of time and brain-disk-space.

Re:Devi: another brilliant mathematical mind

[MickLinux]

No, it starts with an 8.

2^63 = 8 000 000 000 000 000 (base 16).

It's a lot easier to do most math in base 16, I think.

Re:So Guinness not suck now?

[Anonymous Coward]

Actually, Guiness record was produced by the same beer company. Sure, it was sold to someone else, but that happened after the company had hijacked some critics' domains. You could bet some of these hijackers are still running both companies.

My Turn

[Stupidhead]

1 One Thousand
2 One Thousand
3 One Thousand
4 One Thousand
5 One Thousand
6 One Thousand
7 One Thousand
8 One Thousand
9 One Thousand
10 One Thousand
11 One Thousand
12 One Thousand
FVCK!#$

Re:My Turn

[Anonymous Coward]

Ya I know, I could only get to the 12-th digit by then too. Sucks.

The first mentat?

[Rai]

Get this guy some sappho juice.

Re:The first mentat?

[fireboy1919]

It is by will alone I set my code in motion.

It is by the juice of caffiene that thoughts aquires speed, the hands develop shakes, the shakes become a warning.
It is by will alone I set my code in motion.

--Coder's litany.

Re:The first mentat?

[Anonymous Coward]

Sappho juice nothing- Get this guy some beer and a girlfriend.

I so call bullshit

[tomstdenis]

Unless there is some really trivial algorithm for finding 13th roots I totally call bullshit. If it takes him four seconds to memorize a 22 digit number how can he manipulate and find a 13th root for a 100 digit number in just over twice that amount of time?

There has to be a trick to it aside from "thinking really fast"

Tom

Re:I so call bullshit

[kfg]

There has to be a trick to it aside from "thinking really fast"

Well of course, there is. Probably two or three tricks combined. . .plus thinking really fast, as well as having a good memory for numbers.

Walking a tightrope is more than just having "good balance," and it's really just a trick, and not necessarily a very useful one, but. . .

It is still pretty impressive and you can't do it.

KFG

Re:I so call bullshit

[Anonymous Coward]

Trick one: Realize it's a number between 0-9 and work from there.

As time ticks down, you have a 10% chance of getting it right if you flat out guess.

Re:I so call bullshit

[HardCase]

Well of course it's a trick! You know that the first digit is 4 and the last is the last number of the 100 digit number. The guy probably also has memorized log tables up to some ridiculous value which gives him help for another four or five digits. Then I'm sure that there are some other techniques to derive the rest.

This sort of stuff is all trickery of a sort - but so what? It still requires some significant mental gymnastics...I know that I couldn't do it in 11.8 seconds or probably even 11.8 hours. In fact, my calculator would probably be a smoking puddle of plastic if I tried to cheat.

-h-

Re:I so call bullshit

[Anonymous Coward]

Being an acomplished tight-rope walker (as in, i can do it,) I can tell you that it isnt anything but balance.

Unless of course you count putting your feet in the wrong place (i.e. not on the rope) but that qualifies as balance if you ask me.

Get a proper analogy.

Re:I so call bullshit

[Anonymous Coward]

You are assuming that he has to memorize the whole number to process it. Maybe his algorithm does not need this and he can process it part by part.

Re:I so call bullshit

[kfg]

Being an acomplished tight-rope walker (as in, i can do it,) I can tell you that it isnt anything but balance.

Being an accomplished solver of mathematical problems in my head (as in, I can do it) I can tell you that it isn't anything but thinking. That doesn't mean that there aren't tricks of thought that one can learn, if one thinks about them.

The question is, can you walk a tightrope faster than anyone else?

Ah, well, perhaps those of us who can do it faster than you have learned a few analogous tricks of balance.

KFG

Re:I so call bullshit

[Anonymous Coward]

There has to be a trick to it aside from "thinking really fast"

Well, no shit. Shouldn't the author of ltm/ltc see the obvious tricks right away?

ahh

[nomadic]

It's worth noting though that his feat will not be recognized by The Guinness Book Of World Records because of the difficulty of standardizing such mathematical challenges.

That's the problem when dealing with a highly subjective field like mathematics.

Re:ahh

[thegrassyknowl]

There are some very objective fields in the GBOWR - they reward absent-minded and even plain stupid achievements (the most people in a phone booth, for example; even though there is no world standard size person or phone booth) but will not reward intelligence.

There is no real way to say, however, whether this guy cheated or not. It wouldn't be hard to pre-arrange the number with whomever was generating the 100 digit number in the first place, go and calculate the 13th root and memorise it before you are "told" the number and asked to calculate the 13th root. I am not implying that he did cheat, however, just that it is possible if you _really_ wanted to.

It is, on the other hand, hard to cheat when you're shoving pencils in your nose or people in a phone box. They're either in there or they're not.

Re:ahh

[martinX]

Well you could cheat by stuffing the phone box full of dwarves.

Re:ahh

[Omkar]

That's what I thought too. I guess it's not the math part but the human difficulty part. I'm sure you could calc approximately how many steps you need to do a certain task with a set algorightm, but the difficulty of each of those steps varies wildly in human terms. And that, I suppose, is the subjective bit. Is it harder to add 50digit nos or multiply 10digit ones?

Re:ahh

[Anonymous Coward]

Sure, but where do you find a blender big enough to liquify a dwarf?

Re:ahh

[Anonymous Custard]

I prefer the "fattest twins on motorcycles" type of world records.

Re:ahh

[Dirtside]

Request to moderators: Mod down anyone who says "I know I'll be modded down for this."

No... then they'll just demand to be modded up because they're psychic.

News Flash...

[WwWonka]

Gert Mittring, 38, needed only 11.8 seconds to calculate the 13th root of a 100-digit number in his head

In a related bit of odd coincidence to this story, 11.8 seconds is the longest Gert has ever talked to a single female at any one given time.

What he will be doing next week...

[jmcmunn]

Probably breaking codes for some government or another. Someone with talent with numbers and such will catch the eye of someone out there. Could it be that this was just to show off his talent as a sort of "job interview"? Probably not, but I expect he will get some calls about it anyway.

Re:What he will be doing next week...

[Anonymous Coward]

I'd like to see the guy decide in 12 seconds whether a 100 digit number is prime...

Randy

Re:What he will be doing next week...

[Alsee]

breaking codes for some government or another

Yes, I hear the Estonian secret intelligence agency encrypts all of their messages by raising it to the power of 13.

-

Re:What he will be doing next week...

[daniil]

Actually, they use a much different and much more complicated technique:

1. Do everything by hand. This is strictly required.
2. Convert the message into decimal numbers -- a =1 , b = 2,...,y = 32 (using the expanded Estonian alphabet).
3. Modulo all the numbers by (x mod 24, where x = the sum of all the letters in the name of the previous president of Estonia. Currently, x = 132)
4. Multiply the numbers by 1918 (the year Estonia gained independence).
5. Substract 1991 (the year Estonia regained independence)
6. Lose the spaces.
7. Divide this long number into blocks of 24 letters.
8. Reverse these blocks/lines.
9. Transpose the gained matrix.
10.

Re:What he will be doing next week...

[daniil]

10. Don't push the 'Submit' button instead of 'Preview. Grr.
11. Once you're done, burn the results, because by the time you've finished with all this (we ARE talking about Estonians, you know, and they're never been known for their haste), the matter has lost its urgency anyway.

Re:What he will be doing next week...

[Lt.Hawkins]

12. ????
13. Profit?

Re:What he will be doing next week...

[daniil]

Oh, FFS. This is just so damn typical of you Americans: whatever you do, it must turn out profit. Bah.

(Yeah, i have in fact had enough of this "1 do x. 2 ??? 3 - profit!" meme. How did you guess?)

And in other news ...

[Anonymous Coward]

After some months of training, I'm now able to calculate *any* 100-digit root of zero *instantly*!

Re:I can (seriously) do 43rd root of 100 digit num

[Anonymous Coward]

Its a record becuase AP says so?

The future is here

[forgetmenot]

When I hear about people like this I can't help but think of "Dune" and it's Mentats.

I would like to know how much of this ability is genetically determined and how much is due to training and from what age did his "gifts" become apparent.

Either he needs to be stuck into some kinda breeding program (perhaps solving his virginity problem *hyuk hyuk*) or his training regimen needs to be studied and duplicated en masse. Imagine an advanced state-of-the-art military computer system that runs on 3-square meals a day and isn't susceptible to EMP bursts.

Re:The future is here

[Ace905]

Humans are susceptable to EMP bursts, but worse, they're subject to bullets.

Re:The future is here

[Grey_14]

And Current Military computers are not vulnerable to bullets?

Re:The future is here

[TheRaven64]

Not really. We have machines to do this kind of thing for us. I went to school with a few people like this (although not in quite the same league). They tend to do really well until about the age of 14-16, when the ability to reason becomes more important than the ability to calculate.

Re:The future is here

[zallus]

Military computers can be sealed in an airtight room, surrounded by two-foot thick titanium slabs on all sides, buried far below the earth's crust. Doing that to people will quickly cause their super-arithmetical abilities to degrade.

dumb tricks...

[Vellmont]

It sounds impressive, but how usefull is doing something a machine can already do more quickly and efficiently? John Henry learned this the hard way. As others have pointed out there's tricks and shortcuts that people use to doing these calculations, so most of it just amounts to mathematical parlor tricks.

The implicaton is this guy is a genius. Maybe he is, but calculating roots quickly doesn't make you a genius, it just means you know some math tricks. Isn't this just the mathematical equivalent of how many peanuts can you stuff up your nose?

Re:dumb tricks...

[Anonymous Coward]

I'm gonna get me a calculator too!'

Re:dumb tricks...

[Anonymous Coward]

It sounds impressive, but how usefull is doing something a machine can already do more quickly and efficiently?

Like say, woodworking? (Or spelling, in your case.) Fact is people just enjoy doing things. Lots and lots of things. Life is vastly more complex than basic food & shelter & fucking.

Incidently,

genius
1390, from L. genius "guardian deity or spirit which watches over each person from birth; spirit, incarnation, wit, talent," from root of gignere "beget, produce" (see kin), from PIE base *gen- "produce." Meaning "person of natural intelligence or talent" first recorded 1649.

genius
Inflected Form(s): plural geniuses or genii /-nE-"I/
Etymology: Latin, tutelary spirit, natural inclinations, from gignere to beget
1 a plural genii : an attendant spirit of a person or place b plural usually genii : a person who influences another for good or bad
2 : a strong leaning or inclination : PENCHANT
3 a : a peculiar, distinctive, or identifying character or spirit b : the associations and traditions of a place c : a personification or embodiment especially of a quality or condition
4 plural usually genii : SPIRIT, JINNI
5 plural usually geniuses a : a single strongly marked capacity or aptitude b : extraordinary intellectual power especially as manifested in creative activity c : a person endowed with transcendent mental superiority; especially : a person with a very high intelligence quotient
synonym see GIFT

I don't think you've thought very much about "useful" or "genius".

Re:dumb tricks...

[Vellmont]

I don't think you've thought very much about "useful" or "genius".


I think I know what the word genius is intended to mean, especially since I'm the one using the word. You can quote however many dictionary definitions you like, but that doesn't change the fact that most useage of the word genius is using definition 5. Here's the 10 definitions of the word dog for instance:

1 a : CANID; especially : a highly variable domestic mammal (Canis familiaris) closely related to the common wolf (Canis lupus) b : a male dog; also : a male usually carnivorous mammal
2 a : a worthless person b : FELLOW, CHAP
3 a : any of various usually simple mechanical devices for holding, gripping, or fastening that consist of a spike, bar, or hook b : ANDIRON
4 : uncharacteristic or affected stylishness or dignity
5 capitalized : either of the constellations Canis Major or Canis Minor
6 plural : FEET
7 plural : RUIN
8 : one inferior of its kind: as a : an investment not worth its price b : an undesirable piece of merchandise
9 : an unattractive person and especially a girl or woman
10 : HOT DOG 1
- doglike /'dog-"lIk/ adjective

Do you pull that out every time someone uses the word dog? I don't think you've thought very much about word definitions taken from dictionaries.

As far as "usefull" I suppose anything can be usefull to an individual if they find it usefull. If you enjoy woodworking then it's "usefull". If you enjoy stuffing peanuts up your nose it's "usefull". At that point we've diluted down the meaning of usefull to the point where it means almost nothing.

Your analogy is flawed anyway. Woodworking and machines that accomplish the same goal don't produce the same output. Mathematical problems, by definition have to. If they didn't there's a flaw in the methodolgy, or the computer.

As for spelling, I might be concerned if this were my disertation or a letter to the editor of a newspaper. This is slashdot though and minor spelling errors are quite acceptable here. It's only nitpickers that seem to point them out.

Re:dumb tricks...

[EvilSporkMan]

Which John Henry? Your link leads to a disambiguation page.

Re:dumb tricks...

[Vellmont]

Sorry, this one (the steel driving man). It's one of the original man vs machine competitions (if only folklore).

Wizard...

[fourharpoon]

Apparently, most /.-ers don't value this feat highly. Well it makes sense, these geeks don't love computer for no reason :-)

But IMHO, it's a great gift, nonetheless. Heck, I can't even remember my girlfriend's birthday.


~ Sig is not parsed by modder

Gert disqualified and sued!

[G4from128k]

Gert Mittring was disqualified when judges noted a small sticker on his chest in a post-event checkup. It was discovered that he had Intel Inside.

The news set off a legal feeding frenzy. SCO sued Mr. Mittring for using the company's super secret 13th root finder source code. Microsoft then added to the man's woes by suing for patent infringement over Microsoft's patents on 100 digit numbers. RIAA then sued him for including "8675309" in the answer -- obviously a stolen clip from "Jenny" by Tommy Tutone.

Re:Gert disqualified and sued!

[Anonymous Coward]

Presumably he wasn't running an original pentium, though.

I know you were joking, but...

[Quattro Vezina]

The number of elementary particles in the universe is estimated to be around an 80-digit number. It would be impossible to even write every 100-digit number in existance--you'd run out of matter in the universe first. Even if that were possible, just imagine the time it would take to even look at each one...

It's really interesting to think of all the hard limits in the universe caused by things like this.

Imagine

[snnmnd]

Imagine a Beowolf cluster of this guy!

The rules

[strange_attract0r]

It's for a 100-digit number whose13th root is an integer. Read the rules about how it works here

Photo of Gert Mittring here

[Magickcat]

A photo of Gert Mittring can be found here.

Please note his rather tasteful attire.

The page also has information on the actual rules on calculating the 13th root of a 100 digit number.

Re:Photo of Gert Mittring here

[ilyaa1]

The timing begins when the number becomes visible to the competitor and ends at the end of writing the answer.

Which means, that out of those 11.38 sec, he actually had to spend some time writing (or dictating) that answer. Which means that calculation took even less than that.

OK...

Re:Photo of Gert Mittring here

[weighn]

yes, but can he jag chicks?

Re:Photo of Gert Mittring here

[Magickcat]

Take a look at that snazzy outfit. He's made to multiply.

Re:Photo of Gert Mittring here

[weighn]

Take a look at that snazzy outfit.

I MUST have that tie. Really. There's like formulas and stuff on it!

Re:Photo of Gert Mittring here

[rxmd]

A photo of Gert Mittring can be found here. Please note his rather tasteful attire.

I met him last week... You should have seen his attire then. He was wearing a suit and a long shawl, and muddy combat boots. Quite a character.

Re:Photo of Gert Mittring here

[Magickcat]

Ahh, brains and an eccentric dresser - good for him.

13th root

[russ_allegro]

There are 13 thirteen roots of a 100 digit number.

Re:13th root

[ZigMonty]

Sure, but since 13 is odd, the other 12 roots are complex. It's not like the square root, 4th root, 10th root, etc, where you'll get 2 real roots.

11.8 seconds?

[bzBetty]

pppfffft, my 286 can do it faster...

Increasing math ability

[_Hellfire_]

This guy appears to have "superhuman" math ability, and I would imagine that it's just the way this guy's brain is wired that allows him to do that.

I always wonder if there is a condition that works in the opposite way, a bit like dyslexia for reading/writing for maths, a sort of "mathlexia" if you will. Just as dyslexia doesn't mean you're stupid, it's just that your particular model of brain doesn't comprehend words straight away, a person with "mathlexia" can't add up 137 and 48 in their head to save their life, let alone do anything complicated like division or factorisation.

If there is such a thing as mathlexia, I'd say I've definately got it. The funny thing is, I love computers, I love programming (in C among other languages, though a mastering of assembly has persistently eluded my efforts), and I can understand even engineering diagrams and other geeky stuff. I kicked ass in English Literature at high school (even though I didn't particularly enjoy it and it's not where my passions lie); but I cannot do maths in my head if my life depended on it. Even with a calculator I get lost in the process of doing a complicated sum, but I would say I'm at least a half decent programmer. It's not that I have a problem with a logical process, it's the math part that throws me.

Is it just the way my brain is wired? Is there a big secret no-one's telling me that will make this all easy? Am I destined for a life of going "uh huh? righto..." when someone explains a (pure) math concept to me? Or is there some hope for a math dummy like me?

If anyone knows the answer(s) to any of this I would be eternally thankful.

Re:Increasing math ability

[BoneFlower]

"Is there a big secret no-one's telling me that will make this all easy? "

There is a simple trick to math, that sounds bleeding obvious, but it took me years to truly figure out- once I did, it all became really easy.

Math is really easy. Just learn the process, apply it, and you will always get the right answer. You say you have no problem with the logical processes- well thats all math is.

The big secret is that there isn't a big secret. Unless you've forgotten your addition and multiplication tables, or operator precedence and association rules, then going through the process will *always* lead to the correct answer. IF you've forgotten any of those, just brush up on them and you will be set for pretty much any math you run across in normal life(and those things form the basis for even the most advanced base-10 math).

Re:Increasing math ability

[Rangsk]

When I do something like 137 + 48 in my head, I tend to work backwards... it's kind of odd but it's how my brain works (also allows me to do it as I read the numbers, and start giving the answer before I finish adding). So, in this case, I'd immediately see a 3-digit number plus a 2-digit, so I start with 1, the I see 3+4 which is 7, so 17, then 8+7 which is 8+8-1=15 (it's faster for me to do that than remember what 8+7 is since I'm bad at memorizing), so the answer is 185. You may have been exaggerating when you said you can't do that addition in your head, but if you weren't I hope this helped. Something with a lot of carryovers works the same way. For example, 999+999... 18, 198, 1998 done. 547+943.. 14, 148, 1490. As for pure math concepts, they are heavily based in logic, and if you can do computer programming, I really don't see why you wouldn't be able to understand them as well. Maybe you've convinced yourself that you can't understand it, so instead of saying "wait, what was that?" you simply glaze over and say "right, uh huh, yup." Obvsiously, if you miss something important early on, you won't be able to follow the rest of the idea. As for assembly, well, assembly wasn't designed to be written by humans. If you want to write anything worthwhile in assembly, you really need to write out pseudo-code first, then break it down line-by-line. Just a few thoughts.

Re:Increasing math ability

[Anonymous Coward]

>>Is it just the way my brain is wired?.......

Yes. I'm in Mensa, my IQ is in the top 1% of the world, I dislike math, graduated high school in the bottom quarter of my class.

But I earned a BS without studying, I can out-think almost anyone in problem solving, I'm a computer nerd for a BIG computer company.

It's not who I work for, but I "think different". It has it's good points and bad, but the good usually outweighs the bad. Accept it, enjoy it. You are "divergent".

Re:Increasing math ability

[damiam]

That's not entirely true. What's the process for proving a theorem? There isn't really one. It requires a certain amount of creativity and skill to come up with the right steps to go through.

In any case, going through the process is really easy to screw up unless you understand the underlying concept. That understanding (like what exactly does an integral mean?) is what can be hard for some people.

Re:Increasing math ability

[damiam]

999+999... 18, 198, 1998 done.

It's easier for me to do that as 1000+999-1=1999-1=1998.

Just another way to look at it.

Re:Increasing math ability

[Vellmont]

That's not entirely true. What's the process for proving a theorem?


The parent and grandparent were referring to simple mathematical operations like addition and subtraction. You don't require any understanding of the underlying concept to perform the operation. That's why it's so easy for something as incredibly stupid as a computer to do simple mathematical operations.

Re:Increasing math ability

[rcrooksie101]

Math is not an easy subject. There's no one trick that will shed light on how to 'get good' at it. But first realize that this guy is solving a highly specialized problem (the 13th root of a number), for which there are many tricks (using number theory).

Most math isn't about tricks like this or calculations of imposing numbers, but rather more like logic puzzles.

If you want to get better at computing numbers try this. Every time you buy something try figuring out the sales tax ahead of time. When weighing vegetables - figure out the total cost - etc. If that's too hard just try to get it to the nearest dime, then later, cent. I like to have the change out ahead of time - hehe.

Computation is a matter of practice. If you don't use it alot you'll get rusty. If you do it alot you'll figure out shortcuts on your own - and those shortcuts are the first steps in number theory.

There's no easy way to learn math except through practice. Unless of course you are truely gifted. It's said that Carl Gauss (a famous 19th C. mathematician) added up the numbers from 1 to 100 in grade school 'in his head' in a few seconds. Anyone can do it, it just takes a little thought. If you have fun with that problem - pick up a number theory book and enjoy.

Also, Martin Gardner (do a search on amazon) has a few excellent books for the math lay-person, full of mathematical puzzles that will help you foster mathematical insight that I highly recommend. Good luck!

Re:Increasing math ability

[lachlan76]

Try to break it up into smaller, simple problems. You don't try to write some huge program all in main(), do you?

For your example, 137+48, if you learn all the combinations of single digit integers, then you can break it up into:

100 + 000 = 100
30 + 40 = 70
7 + 8 = 15
answer = 100 + 70 + 15

Because you have multiples of ten for the most part, it is a lot easier.

But this is just my way, it may not work for other people.

Re:Increasing math ability

[jpkunst]

a sort of "mathlexia" if you will

That would be "dysmathia" (the "disorder" meaning resides in the dys- part of the word), but the correct term is dyscalculia. See http://en.wikipedia.org/wiki/Dyscalculia

JP

Re:Increasing math ability

[peter_gzowski]

I always wonder if there is a condition that works in the opposite way, a bit like dyslexia for reading/writing for maths, a sort of "mathlexia" if you will.

There is such a condition. It's called dyslexia. Dyslexia symptoms include difficulties in mathematics, particularly arithmetic. Sometimes this particular difficulty is termed discalculia.

In my limited experience helping dyslexics with math, I've found that visual aids such as hand tricks work great, and that dyslexics have little trouble with visual math disciplines such as geometry.

Re:Increasing math ability

[TheRaven64]

Your `answer' should again be broken up into:

5 + 10 + 70 + 100

When doing this, adding each subsequent digit only changes a single value, making it very easy to solve. Of course, it would be better if you did this from the start (as you should have been taught in school. I seem to remember doing this at age 3 or 4):

7 + 8 = 15
15 + 30 = 45
45 + 40 = 85
85 + 100 = 185

At each stage, you are adding a number in the form n x 10^x to your existing solution (where n is a single digit), which is very easy - particularly since your existing solution is in the form of m x 10^x, where m is a single digit followed by a decimal point (and x has the same value in both). This is a very simple iterative process that can be done very quickly. You can make it even faster buy memorising what teachers refer to as `number bonds' (i.e. the sum of every combination of single digit numbers) - again, something most people do while small children.

To put this in computing terms, you create a table of single digit sum values and then iterate along your input numbers calculating results. I'm always amazed by the number of people who seem to be able to program computers, but have no idea how to program their own brains.

Re:Increasing math ability

[TheRaven64]

Thank you. There seems to be a great deal of confusion in this discussion between mathematics and arithmetic. Having said that, automated theorem proving is a highly active research area (particularly within my department). Additionally, there are a number of techniques that can be applied to proofs in almost a rote fashion (e.g. induction, proof by contradiction, etc), although they don't always work in a particular case.

Lucky Guess

[Anonymous Coward]

Maybe it was just a lucky guess.
What are the odds?

Here's a challenge

[tomstdenis]

That involves some memory...

Fastest time to find the char-2 differential profile of a random bijective 4x4 look up table. No gimmicky tricks there just pure nlogn work in your head ;-)

From what others have posted and I've read on the net the 13th root is a trick to a large part. The leading digits are a strong indicator of the value of the root, etc, etc, etc.

Or something with more practical implications... fastest time to perform an inverse cosine transform [type used in MPEG video] of an 8x8 matrix in your head. ;-) Nothing like decoding JPEGs with only your mind.

Tom

To put it into perspective

[Highpriest]

This is a 100 digit number: 19283740592837485932081293847560293618273458192031 17346932745397452409864082460814617651293753975329 Now. Get the 13th root of it..... In 11 seconds...

Re:To put it into perspective

[mothz]

43383282.2

Re:To put it into perspective

[Anonymous Coward]

That is a little harder than finding the 13th root of the 105 digit number: 10^104, where the 13th root is 10^8. I thought it was something that could be done very easily. My bad :o)

I can do it too

[karvind]

Let me get my calculator. Aa aa ok I cannot enter the exact number it doesn't have enough digits. Bill G said 4 digit number should be enough for everyone.

Re:"memorizing 22 random digits in just four secon

[Class Act Dynamo]

Well, since there are only ten digits, I think ordering would have to be relavant. Otherwise, he could just count how many occurences of each digit there are, which would certainly not be quite as impressive.

High pi

[dexter riley]

I read somewhere that you only need about 50 digits of pi to describe a circle the size of the observable universe to within the diameter of a proton, let alone a chocolate donut.

This isn't to say that 1350 digits wouldn't be useful! If you ever wake up in an alternate universe (you were warned about operating quantum machinery while drunk!) just look up pi in a math book. The degree of trouble you're in could correlate to the digit at which your memorized value, and the local value of pi, diverge.

If pi only diverges after 1000 or more digits, you're probably alright, except for having to re-memorize pi.
If pi diverges after 100 digits, there may be some minor historical divergences, like, say, President Nixon being impeached, or Bush winning a second term. The mind boggles!
If pi diverges after 30 or 40 digits, look out the window. Do dinosaurs roam the earth? Since you're surrounded by ruthless, math-book-publishing carnivores, consider donating yourself to the primate house of the zoo.
If local pi begins with a number other than 3, you should start to get worried, or maybe implode.

Re:High pi

[gardyloo]

For another such bit of trivia (and this one's much easier to work out), give this riddle to your friends:

Imagine a (perfect) sphere the size of Earth, with a rope tight around some equatorial line, circumnavigating it. If you wanted to have the rope one meter above the ground all the way around the sphere, how much rope would you have to tie on to the end to do so?

The answer, as it's very easy to see after knowing the answer, is 2Pi meters, or about 6.28 meters. Most people, without checking the math, are very surprised that it's such a small number.

Just a tid-bit.

Re:High pi

[Prune]

No personal offence intended, but that really was kind of lame. [Note to moderators: consider the parent post carefully before modding me down.]

Re:High pi

[Prune]

No personal offence intended, but that really was kind of lame. [Note to moderators: consider carefully the parent post before you mod me down.]

Re:High pi

[LnxAddct]

For those of you curious of the math... its simple:
C_{1}=Pi*D
C_{2}=Pi*(D+2)
C_{2}=(Pi*D) +(Pi*2)
C_{2}=C{1}+Pi*2
So the new circumferance is the old one plus 2*Pi.
Regards,
Steve

Re:High pi

[Nyh]

I read somewhere that you only need about 50 digits of pi to describe a circle the size of the observable universe to within the diameter of a proton, let alone a chocolate donut.

Well, let us see:
radius universe: about 15e9 lightyears
radius proton: 1.2e-15 m

circle with the size of the universe divided by diameter proton:
2*pi*15e9*365*24*3600*300000000/(2*1.2e-1 5)=3.7e41 .
So 42 digits of pi will do.

42? Where did I see this number before?

Nyh

Re:High pi

[indigeek]

Ramanujan was the first to ask that question (to his students in his private classes)
Ramanujan : Self-taught indian mathematician who used to believe that a goddess used to teach him maths in the sleep. Apparently rediscovered the binomial expansion of e while a teenager.

Re:High pi

[Anonymous Coward]

Or if it equals 3.2, 4 or 3.23, you might be in Indiana.

Re:High pi

[d_strand]

Well, let us see:
radius universe: about 15e9 lightyears
radius proton: 1.2e-15 m

circle with the size of the universe divided by diameter proton:
2*pi*15e9*365*24*3600*300000000/(2*1.2e-1 5)=3.7e41 .
So 42 digits of pi will do.

42? Where did I see this number before?

Not to be too anal (well ok, i admit i like it) but your size of the universe is off. The age of the universe is about 15e9 years, but latest estimates of its size is around 100e9 = 1e11 (possible because of 'inflation' during big bang) so 42 wont quite cut it. Too bad cause that would have been really cool...

Re:High pi

[Q Who]

Not to be too anal (well ok, i admit i like it) but your size of the universe is off.

No, it's not - the OP specifically said observable universe.

Re:High pi

[Eosha]

I heard the same thing in high school, only it was 36 digits. I figured I'd never need to know more than that, so I spent a couple days memorizing pi to 36 places, and I've known it ever since.

Still hasn't got me laid...

Re:High pi

[statusbar]

Funny, but it brings up a thought I had a while ago.

I believe that PI is just an abstract concept - PI is not a measurement - and as such has nothing to do with the properties of the universe you are in. Even if the universe is a single dimension or even if the universe's space is heavily warped. The people living in these universes would either have no use for PI or would have some sort of compensation factor.

I belive that the algebra/math behind the concept of PI (and 'e', etc.. ) is a constant across multiverses.

Therefore I believe pure math = God. ;-)

--jeff++

Re:High pi

[d_strand]

I stand corrected :-)

Re:High pi

[blazin]

Was it The Man Who Loved Only Numbers?

That's where I read that.

Oh come on now.

[laughingcoyote]

I can do the 23rd root of a 163 digit number in 5.8 seconds, and I wasn't even trying. I've climbed Mt. Everest in an hour and a half. I can rewrite the Linux kernel in under an hour. I can count up to ten thousand coins in no more than a minute.

And yet, curiously, it takes me almost...-checks watch- five minutes to make a stupid, useless post on /. Strange eh?

Re:Oh come on now.

[Anonymous Coward]

I can do the 23rd root of a 163 digit number in 5.8 seconds, and I wasn't even trying. I've climbed Mt. Everest in an hour and a half. I can rewrite the Linux kernel in under an hour. I can count up to ten thousand coins in no more than a minute.

But how long does it take you to get a date?

Re:Oh come on now.

[laughingcoyote]

I have 3 kids. Do THAT math. :)

Re:Oh come on now.

[Anonymous Coward]

I have 3 kids. Do THAT math. :)

So in 16 to 24 years? Depending on the age of the kids... how you feel about leaving them alone... when they leave home... and if you decide to date someone else other than your wife :)

If I recall...

[gravteck]

I don't remember if this was the same guy I saw on TV. But the guy I saw was performing large multiplications and finding large roots in front of an elementary school class. They later showed doctors or scientists doing brain imaging on him while he solved math problems. What they found was that he was using parts of his brain that most people utilize during visualization (not sure how they were able to separate it from him actually seeing something). He said he visualizes the number in his head and then he can perform various manipulations on them and he can "see" the math work itself out. Obviously some is probably genetic, but he also commented on practicing his methods for 5-7 years. He also appears to not be the only root master.

Re:If I recall...

[prash_n_rao]

Yes... maybe this will help you understand how this link below help you understand how this can be done ;-)

http://www.gpgpu.org/

Re:If I recall...

[Lorean]

Curious. When you say he 'visualizes' the numbers does that mean he visualizes their arabic representations or does he have his own visual abstraction?

Re:If I recall...

[Ieshan]

Much of this is practice and algorithm, just like the people who are expert rubik's cubers.

It's not really all that much different from athletics - there's a certain amount of "natural talent", and then there's a good deal of practice required to actually become a competitive athlete. Muscle memory isn't much different from algorithm memory. I think it might be an interesting psychological study.

Re:If I recall...

[m50d]

The book "Anvil of Stars", by Greg Bear, has an idea of something like this in it, and is a pretty good book anyway. Think about it - the uncouncious trig you do to work out how far away something is, and the quadratic you solve every time you catch a ball, are much faster than you could do "manually".

Re:If I recall...

[mpnolan]

Well, the trig used for calculating how far away something is and the quadratic in trajectory physics are tools invented by us to describe and predict those two things. Our brain does not perform those same algorithms that we consciously do. It seems like that might be what you mean to say, but it was written in such a way that it seems you think our brains actually solve quadratic equations in the same way we do, only much faster.

Re:If I recall...

[m50d]

No one really knows how the brain works, and so far I've only really seen one way to solve a general quadratic equation. So I do think our brains actually solve quadratic equations in the same way we do, only much faster. If you can think of another way the brain would do it I'm prepared to be convinced.

Re:If I recall...

[mpnolan]

Think about an object traveling that does not follow the trajectory described the quadratic equation. For example, a piece of paper dropped from a building.

gt^2 + v_0t + h_0 doesn't apply here. However, we are still able to move around and grab the paper out of the air! And I think these brain functions are apart of the same class as the ones used to catch a baseball flying into left field are.

Re:If I recall...

[Anonymous Coward]

Hmm... obviously, these people have high-speed VRAM!

To how many significant figures?

[jwise]

And how much about the problem did he know in advance? Did he know it would be a 13th root of a 100-digit number? Did he know that the number would be a perfect 13th power of an integer? I find it impossible to believe he calculated a 13th root of a 100-digit number in 11.8 seconds without knowing any of these things. Knowing all of them makes the problem a lot easier.

The 13th root of a 100-digit number will always have 7 digits. If you memorize the first few digits of the 13th powers of numbers between 49 and 58 and you are given a 100-digit number, then you immediately know the first 2 digits of the 13th root. Memorize the initial digits of 13th power of numbers between 491 and 588 and you immediately know the first 3 digits. By memorizing the terminal digits of 13th powers of numbers less than 100, you could similarly immediately get the last 3 digits. That leaves 1 digit to compute, which is a slightly less impressive-sounding feat for 11.8 seconds. It's not a trivial calculation, though, and not at all shabby for 11.8 seconds.

Jonathan

Re:To how many significant figures?

[Echidna9686]

There was a previous post referring to this site describing the rules. He would have therefore known about the problem beforehand. It's also interesting to know that he attempted it before with a 39.0-second time, beaten only by Alex Lemaire's 13.55 seconds.

Uh oh!

[Ummu]

Lets kill him before people start cloning his brain and making computers useless...

(all that training...)

silly question begging to be asked

[calculadoru]

at a math museum in Giessen

a math museum ??? can someone explain what a math museum contains? surely not the pickled brain of Leibnitz next to Pascal's toothbrush?

Re:silly question begging to be asked

[rossdee]

Maybe "Napier's Bones"

(Google for it)

Re:silly question begging to be asked

[Vario]

I've been to the math museum in Giessen. It contains a lot of interesting stuff about the Golden Ratio, Calculus, some experiments to show Pythagoras idea of a^2 + b^2 = c^2, etc. Prof. Beutelspacher came up with the idea, he has written some very good books about linear algebra and knows how to explain mathematics without scaring people off.

If you are ever near Giessen in Germany don't miss it. Here is the link:

http://www.mathematikum.de/

Re:silly question begging to be asked

[TheRaven64]

Napier's Bones (also referred to as Napier's Rods), and the resulting latice method of long multiplication is something I honestly can't believe isn't taught in more schools. I was taught it aged 9 (by a teacher who died of cancer a little under a year later), and couldn't believe how easy it was. Every other class on long multiplication I had focussed on `classic' long multiplication and multiplication by factors (which is just a general case of the classic method). The bones / rods themselves are not required, since it's fairly trivial to memorise their contents. In the interest of educating the Slashdot masses (and because I have several better things I could be doing and want to procrastinate for a little) I will explain it here:

The first step is to write the two numbers on the top and right hand side of a grid, with diagonal lines running from top right to bottom left. As an example, I will use the numbers 123 and 456:

__1___2___3__ x
| / | / | / |4
| / | / | / |5
| / | / | / |6

Next, in each square, write the product of the digits from the two numbers being multiplied that correspond to the square, the tens above the diagonal, and the units below:

__1___2___3__ x
|0/4|0/8|1/2|4
|0/5|1/0|1/5|5
|0/6|1/2|1/8|6

Finally, add up the digits along the diagonals. Unfortunately, the limitations of ASCII have made it less than obvious that the bottom left of each diagonal line should continue into the top left of the square below it and to the left. Start on the bottom right, and carry any tens or hundreds into the next column or two.

___1___2___3__x
0|0/4|0/8|1/2|4
5|0/5|1/0|1/5|5
6|0/6|1/2|1/8|6
____0___8___8

The answer is then read off; (0)56088.

This also works in other number bases, and a cursory examination of it in binary leads to a neat derivation of some optimisations for multiplying binary numbers that are commonly used by microprocessors.

Re:So Guinness not suck now?

[Anonymous Coward]

DOH! I bet a beer company could help out it's drinkers who constantly argue (while drinking) about who's the greatest this, or the longest that, or the fastest other thing by coming out with a book of world records...... Like the Guiness beer company already did... ...Apparently not all slashdot readers (lile the hapless poster to whom I reply) know this simple fact. I type it again DOH!

Simpler than that

[Clueless Moron]

The root is not allowed to end in a zero, because that would have the result end in thirteen zeroes which makes it, um, so much simpler I guess.

That leaves you with a mere... 7,193,306 possible roots to memorize.

I don't know how they do it, but I am familiar with modulo-10 math "tricks". For example, did you know that if you add up the individial digits in any number and the result is divisible by 3, then the original number is divisible by 3? For example "621". 6+2+1=9, and so 621 is divisible by 3 (Try it: 621/3=207).

13th root has similar magic: the 13th root of any number will have the same last digit as the number you are trying to take the root of. For example, the 13th root of 2235879388560037062539773567 is 127. Notice that they both end in 7. An integer and its 13th power always ends in the same digit. Try it.

The point is, that little trick itself reduces the problem space by a factor of 10 right there. So I'm assuming they've studied and learned further tricks like these. Ask them for the 11th root of the same number and they'll probably come up completely blank.

Re:Simpler than that

[Anonymous Coward]

So what you're telling me is that the last digit in the 13th root of say, 1, is ... *counts* ... 1! Holy shit!

Re:Simpler than that

[Alsee]

Ask them for the 11th root of the same number and they'll probably come up completely blank.

Of course they 'd blank, the 11th root of a perfect 23rd power would be an infinite decimal unless the number happened to be a perfect 23*11 = 251st power.

And no, there are no 100 digit perfect 251st powers. 2^251 is 76 digits, and 3^251 is 120 digits.

-

A mild aside

[Anonymous Coward]

I've read that Jackie Chan doesn't make references to his wife, or let his publicists mention her so his female (and some male, I guess) fans don't become too depressed. I see that slashdot readers aren't immune to this, given the number of virginity jokes floating around.

How many swords will have geeks falling on them if Asia Carrera (or insert your favorite pretty woman here, pun may or may not be intended) were to issue a press release saying "Yeah, but he can barely calculate 84 digit squares when I'm with him. With me and his equally hot wife, uh, distracting him at the same time, he's lucky to top 68 digits."

HOWTO Calculate day of week for any Gregorian date

[stiffneck]

clicky

Rapid math tips and tricks by Edward Julius

[Spoing]

This is an amazing book. It will make you a math wiz even if you are an ace or suck at math. Just put in the time. It will even give you some appreciation for how numbers 'feel'.

Cheap new. Even cheaper used (check Amazon).

The book is thin and has a white cover with blue and red lettering.

method to calculate the day of the week!

[GreenPenInc]

Absolutely. :) Let's see if I can type this by the end of the lecture!

First, figure out the "year number". This part -- and the month number -- take some practice. Here's the first few to get you started:
1900 - 0
1904 - 5
1908 - 3
1912 - 1
1916 - 6
1920 - 4
1924 - 2
1928 - 0
And it repeats thusly. Note that the "year number" starts at 0 for the beginning of the century, and is decreased by two (modulo seven) every leap year.

In case you're interested in the other 75% of the time, simply add one to the year number for every year you add. Thus, 1901 becomes 1, 1902 becomes 2, etc.

The "month" number requires memorization of another table, which cannot be recalculated as quickly as the year number:
Jan - 0
Feb - 3
Mar - 3
Apr - 6
May - 1
Jun - 4
Jul - 6
Aug - 2
Sep - 5
Oct - 0
Nov - 3
Dec - 5
Add the month number to the year number. If your year is a leap year and your month is January or February, subtract 1.

Next, add the day number. The day number is the day. :P

Now, add or subtract sevens as necessary until you end up with a number between 0 and 6:
0 - Sunday
1 - Monday
2 - Tuesday
3 - Wednesday
4 - Thursday
5 - Friday
6 - Saturday
The result will be the day of the week.

If your desired date does not begin with a "19", you have to add a century number as well. I believe 2000 is a leap year, since every 100 years is not but every 400 years is. Thus, the century number of 2000 is 6 (or, equivalently, -1). 1800 is 5, 1700 is 3, etc. (I am not certain of these.)

As an example, today's year number is 5, the month number is 3, and the day number is 24. After compensating for the century by subtracting 1, we obtain 31. This reduces to 3 (by subtracting 28), which corresponds to Wednesday. Since it is Wednesday, and since I am in a large empty room, I further deduce that the lecture has ended.

Re:method to calculate the day of the week!

[Zach Garner]

You know, that reminds me of the time I caught the ferry over to Shelbyville. I needed a new heel for my shoe, so, I decided to go to Morganville, which is what they called Shelbyville in those days. So I tied an onion to my belt, which was the style at the time. Now, to take the ferry cost a nickel, and in those days, nickels had pictures of bumblebees on 'em. "Give me five bees for a quarter", you'd say.

Now where were we? Oh yeah - the important thing was I had an onion on my belt, which was the style at the time. They didn't have white onions because of the war. The only thing you could get was those big yellow ones...

Re:method to calculate the day of the week!

[Anonymous Coward]

I look at my digital watch. GG.

Re:method to calculate the day of the week!

[Anonymous Coward]

Try the Doomsday algorithm, it's easier in practice.

Doomsday=The last day of February.
If you can calculate the last day of February of any given year, you can figure out the day of week for any other day within that year.

First, to figure out Doomsday of a particular year, you divide the last 2 digits of the year by 12. Add the integer result with the remainder, and the integer result of the remainder divided by 4. For example, if it were 2005, you would divide 05 by 12 (=0, remainder 5), and divide the remainder by 4 (=1). 0+5+1=6. Now take this number and shift the day of week of the basis day of week by that many days. (In this millenium, the base is Tuesday. Two-Thousand=Tue. is a good mnemonic to use.) In this case, Tuesday shifted by 6 is Monday.

Now all you need to remember is that for all the even months from April to December (month 4, 6, 8, 10 and 12), the same day as the month (4/4, 6/6, 8/8, 10/10, 12/12) are the same day-of-week as that year's doomsday. You can calculate the rest of the days based on this pretty easily. For the even months 5, 7, 9 and 11, just remember the mnemonic "9 to 5 working at 7-11!" 5/9, 7/11, 9/5, 11/7 are all the same day of week as doomsday. The last day in February is doomsday, and the day after doomsday (March 1) is doomsday +1, so you have March. For January, it's January 3rd, except on leap year when it's Jan. 4th.

Okay, so, 2005, August 10th, for no good reason but an example. As shown above, we already know that doomsday 2005 is Monday. August 8th is also Monday. Add 2 days, and we know August 10th is Wednesday. Cool, eh? (/me double checks calendar to make sure there weren't any stupid mistakes there...)

It sounds a bit complicated, but there's very little in way of memorizing random numbers. If all you're interested in is being able to tell the day of week of any year in the 1900's and 2000's, just remember that Doomsday 1900 is Wednesday, and Doomsday 2000 is Tuesday. And the rest is just playing around with numbers in your mind!

Re:method to calculate the day of the week!

[O-SUSHi]

You can also look at the calendar :)

Re:method to calculate the day of the week!

[Anonymous Coward]

The century number about 1800 and 1700 is wrong.
An easy way to calculate it is:
((-century number) + 19) (mod 7)

where century number is 19 or 18 or 20, instead of 1900,1800,2000.

You can obviously add any number equal to 19mod5 instead of 19.

In this way, 2000->6 and 1900->0 but 1800->1 and 1700->2

Using these parameters, the 6th January 1800 is Sunday, the right answer.

In each way, thanks for the nice trick

Re:I can (seriously) do 43rd root of 100 digit num

[Smurf]

I practiced and could calculate 43rd root of a 100 digit number 1 to 3 seconds.

Well, I guess that's not so outrageous depending on the precision you need. All the 43rd roots of 100 digit numbers are greater than 200 and less than 212, so if you only need integer precision you only have 13 choices. And memorizing 12 thresholds is not that hard.

This is not as difficult as it sounds.

[e_lehman]

The 13th root of a 100-digit number is an 8-digit number. Here's how YOU can find TWO of those 8 digits in an instant.

1. The leading digit is ALWAYS 4.

2. The last digit of the 13-th root of N is always the same as the last digit of N.

(The first fact follows because Floor[N[(10^100 - 1)^(1/13)]] = 49238826 and Floor[N[(10^99 - 1)^(1/13)]] = 41246263. The second holds because N^13 is congruent to N modulo 10.)

With minimal practice, you can get the second-highest digit from the magnitude. Beyond that I can only speculate what he's doing. But by taking an alternating sum of the digits, you get its value mod 11, which gives you the value of the root mod 11, which buys you another digit. Now you're halfway there...

Re:This is not as difficult as it sounds.

[godblessthenet]

Of course, to be fair, it should be noted that the above poster is a postdoc lecturer at MIT who is teaching Mathematics for Computer Science this semester and wrote the course notes, including a substantial portion involving number theory.

Oh God, now that I think about it . . . you're putting this on the final, aren't you? NOoOOOooOooOoOOoO!!!!!

Re:The other story disappeared!

[Anonymous Coward]

We have always been at war with Eurasia. Eastasia is our ally.

Some of the methods used

[pvg]

Are described here. Rest of the site is also informative and insane.

http://racine13eme.site.voila.fr/100digang.htm

-pvg

Never mind...

[The Real Nem]

Never mind the time it takes to write or say the response to any significant digit.

Re:I can (seriously) do 43rd root of 100 digit num

[Anonymous Coward]

It reminds me another story. When I was in vacation on Vulcan, Spock teached me (seriously) a way to quickly calculate the 97th root of 500 digit numbers. Well, you know, it's not that hard.

factorize 100-digit composite number

[Anonymous Coward]

is there anyone who can factorize 100-digit composite number? NSA will surely want to hire you :D

Repost?

[EvilSporkMan]

Bush DID win a second term. *tear*

Re:Repost?

[Anonymous Coward]

Nope. The first time around Gore won! *ka-ching*

Re:Repost?

[ChairmanMeow]

*Checks current value of pi*

Oh shit...

Re:Repost?

[Anonymous Coward]

In an alternate universe, I guess. By the way, did you know that Michael Moore won an award?

Re:Repost?

[Angafirith]

Perhaps he meant the other Bush?

proof?

[Deanalator]

Im confused as to how you can prove that you did the calculation in 11.8 seconds, wouldn't it take longer than that to write it down? You are looking at a 50 digit number, so at that rate you would need to be writing down 5 numbers per second even if it only took you 1.8 seconds to realize the answer.

On the other hand it would not be superhumanly hard to come up with the first number in 11.8 seconds, and then write down the rest as you calculate it. The same thing applies to saying it outloud.

Re:proof?

[Deanalator]

with further caffine, I realize that the number will only be 8 or so digits long, and I suppose that would only take 3 or so seconds to say. That makes things a bit simpler, there are quite a few tricks you can do with that, for example the last digit of your 100 digit number will be the same as the last digit of your answer etc.

Making it a bit Simpler, Its a Integer Raised^13

[Shanemoe]

The Rules

1. The record is a standard test of straightforward mental calculation for high order integer roots. The calculator should perform the calculation in his/her head without the aid of any other person and without using a calculating machines, computers, etc. nor may the calculator write the numbers down.
2. The number whose 13th root is to be calculated should be randomly selected by computer immediately prior to the calculation and should be displayed to the calculator on a computer screen, board, screen or similar. It is important that the given number is the 13th power of a integer number which belongs to the interval 41246264 49238826 and whose last digit is not 0.
3. The calculator should write down the answer.
4. The timing begins when the number becomes visible to the competitor and ends at the end of writing the answer.
5. In some cases, the calculator may dictate the answer - then the timing ends as the calculator finishes dictating the answer.
6. Two stop watches should be used: it would be appreciated these stopwatches record in minutes and seconds and tenths of a second rather than hundredths of an hour. At the end of the attempt the time should be taken as an average of the two watches.The name of the person making the attempt should be given, along with the date and place.

322 sec Willem Klein (Netherlands) 19- 9-1975 Amsterdam
231 sec Willem Klein (Netherlands) 8-11-1978 Stockholm
129 sec Willem Klein (Netherlands) 6- 5-1980 London
116 sec Willem Klein (Netherlands) 13-11-1980
88.8 sec Willem Klein (Netherlands) 7- 4-1981 Tsukuba, Japan
39.0 sec Gert Mittring (Germany) 26-05-1988
13.55 sec Alexis Lemaire (France) 10- 5-2002 Villers-Marmery, France

Re:I can (seriously) do 43rd root of 100 digit num

[Anonymous Coward]

The 43rd root of a 100 digit number has a fairly small soluttion set.

Uh oh

[dexter riley]

Does anyone have a math book I can borrow? I really need to look something up.

Re:Uh oh

[mdielmann]

You are my hero. I'm glad I was at home when I read this, and your parent post.

Re:Nobody dies a virgin...

[Anonymous Coward]

And you get the award for "LAMEST POST OF THE DAY!" yaaaaaaaaaaaaaaaaaaaaaaaaaay!

I realise you're just trying to inject a bit of hope into your life, but hey - deal with it - go and buy a "date" with a hooker tonight - you owe it to yourself. That way you really won't die a virgin.

I've seen the movie already

[Anonymous Coward]

Rain Man

Roomie in College

[AlexTheBeast]

I roomed with a guy in college who would calculate a 10 digit by 10 digit multiplication in his head throughout the day on weekends. He would be grilling or watching TV and you would see him get him and write down 1 digit of his answer.

In grade school he had memorized 52 decks of shuffled cards in some insane short period of time. The teacher would ask him what the 12th card of the 17 deck was... and he would start listing them forward and backward from there.

We often went to the casinos with him. He would card count and we just would bet whatever he would bet. We would all make a $100 or so and leave. He was always afraid of getting caught.

Some government agency approached him for running sets of numbers from point a to point b. They liked the fact that he could just put all those digits in his head without a papertrail.

Last I heard of him, he was avoiding math as much as possible... he enrolled in some DO program in a medical school somewhere. Numbers came too easy for this guy... and he knew he would go crazy if he went into a math field.

So now he's a doc somewhere. Probably calculating 10 by 10 digit numbers in his head as he examines you...

Re:Roomie in College

[Crayon Kid]

So now he's a doc somewhere. Probably calculating 10 by 10 digit numbers in his head as he examines you...

OK now that's creepy. If I ever see my dentist stop with his eyes glazed and scribble down a digit I'm outta there.

Re:Roomie in College

[SamSim]

Memorizing and regurgitating and manipulating numbers is a very different skill from mathematics. These are things which computers are very good at - things which we DESIGN computers to be good at so we waste minimal time on such trivialities and work on the stuff which a computer can't do, the stuff which maths is really about: logical reasoning with abstracts.

My point is that just because he's good with numbers doesn't mean he'd enjoy (or be any good at) mathematics. Also, mathematicians can't count.

Re:Roomie in College

[Anonymous Coward]

Also, mathematicians can't count.

This is true. I know one professor that can whip up proofs for functional analysis in a jiffy, but give him 12*7 and he's stuck.

Most mathematicians view evaluation of d/dt(sin(t)) as arithmetic.

Re:Roomie in College

[Wescotte]

In grade school he had memorized 52 decks of shuffled cards in some insane short period of time. The teacher would ask him what the 12th card of the 17 deck was... and he would start listing them forward and backward from there.

How long was he able to retain this information? If I asked him wha thte 17th card was say hour, day, week or year later would he know?

Wonder if he can factor primes.

[Anonymous Coward]

I bet the NSA try to own a few of these.

Hang on a sec...

[rkuris]

Did the article say what the BASE of the ten digit number was? Binary?

Re:"memorizing 22 random digits in just four secon

[DanteLysin]

Reading this article reminds me of a fellow I worked with when I was younger. He could compute mathematical equations such as 56*83 or 123*281 in his head in just a few seconds. But if you asked him, what's 84-21, it would take him forever.

He was autistic and his brain was just "wired" differently from the "norm".

Re:I can (seriously) do 43rd root of 100 digit num

[Anonymous Coward]

"Onlookers with electronic calculators needed more time to solve the problem that Gert Mittring figured on his own, with two umpires checking the time, at a math museum in the small German town of Giessen near Frankfurt in western Germany." Per the article.

Oh yeah? Well they haven't dealt with me and my overclocked ram expanded preprogrammed TI-92!

Really?

[Anonymous Coward]

Last time *I* finished something in 11.8 seconds, my girlfriend said it wasn't something to be proud of. .... fine, so she was imaginary. But still.

Quick!

[uberdave]

What's the 13'th root of 2^13?

Re:Quick!

[adolfojp]

42?

Cheers,
Adolfo

Re:Quick!

[Aerion]

3, for extremely large values of 2.

Re:Quick!

[BlueYoshi]

I got integer overflow :((

Re:Quick!

[Anonymous Coward]

Well that only took... 2 hours...

My Amazing Nephew

[uberdave]

My brother taught is toddler how to spell.

Tom: Hayden, can you spell "encyclopedia"?
Hayden: Yes
Tom: Can you spell "chrysanthemum"?
Hayden: Yes

no

[Anonymous Coward]

the number was 1*10^100

Please...

[temojen]

What are the roots of this product of 2 large primes?

Time?

[wrathcretin]

"4. The timing begins when the number becomes visible to the competitor and ends at the end of writing the answer."

This guy couldn't have possibly been able to even write down his answer in 11.8 seconds. I see the catch as being that the clock stops when you begin writing your answer, at which point you have a decent idea of what the answer will look like (ends in the same digit, starts with a 4) and with some seriously superior mathematical ability, its probably at least attainable to do it in 11.8 seconds, but if the clock stops when you start writing...
That, or as its the average of 2 clocks, maybe noone started the second one...thats 23.6 seconds.

Re:Time?

[InfiniteWisdom]

This guy couldn't have possibly been able to even write down his answer in 11.8 seconds
The 13th root of a 100 digit number is 7 digits long. Most kindergarten kids would be able to write down 7 digits in 11.8 seconds.

I see the catch as being that the clock stops when you begin writing your answer
What on earth are you talking about? Your own quote says it ends at the END of writing the answer!

Re:Time?

[CProgrammer98]

RTFM....
and ends at the end of writing the answer

He cheated!!!

[rice_burners_suck]

The Associated Press reports that Gert Mittring, 38, needed only 11.8 seconds to calculate the 13th root of a 100-digit number in his head at a math museum in Giessen, a small town, located in western Germany.

Wrong, you IDIOTS! He didn't compute Jack Schitt in his head. All he did was memorize every root of every number, and when they asked him, he waited 11.8 seconds, to make it look like he was thinking, and then he told them the answer.

Nobody can compute that kind of thing in their head.

Re:He cheated!!!

[CProgrammer98]

do you KNOW how many 100 digit numbers there are???
There's ummmmm a LOT :)

Maybe he didn't

[Odkin]

Maybe he didn't memorize the 100-digit number within 11.8 seconds but was simply told what to do with it when the clock started ticking.

Pi yes I want a piece blueberry is superb

[MickLinux]

Pi? yes, I want a piece; blueberry is superb.
Pi = 3 . 1 4 1 5 9 2 6

That's the one I always used. Of course, yours is better.

Re:Pi yes I want a piece blueberry is superb

[anethema]

if you're stopping there the last digit should be a seven.

Re:Pi yes I want a piece blueberry is superb

[CProgrammer98]

Obviously, his pi is undercooked....

Re:Pi yes I want a piece blueberry is superb

[MickLinux]

if you're stopping there the last digit should be a seven.

I'm aware of that. However, I tend to remember that fact by remembering an additional 535.

The useful thing about that trick is that it got me the first seven decimal places, which goes a long way towards filling up a calculator screen.

Since most problems only require 3-4 digits of accuracy, tops, and pi is sometimes awkward on the calculators I've had, it's been a great convenience to me.

That said, I enjoy the Quantum Mechanics version a lot more.

Well...

[Anonymous Coward]

He does hold the world record for memorizing 22 random digits in just four seconds."

He's not getting within 20 feet of my credit card.

Re:High pi (you need a lot less than that)

[rcrooksie101]

As the best measurements of fundamental constants are on the order of 20 or so decimal places, any more precision than that is (physically) insignifigant.

Cube root of 6 digit number

[SiliconEntity]

Here's one I used to be able to do. With a bit of practice, you can instantly tell the cube root of any 6 digit number, if the root is an integer. The secret is that the answer will be two digits, and the right digit matches the right digit of the starting number, unless it is one of the pairs 2-8 or 3-7, in which case it is the other member of the pair.

The left digit can be found by memorizing the cubes of the numbers from 0-9: 0, 1, 8, 27, 64, 125, 216, 343, 512, 729. Compare the left 3 digits of the 6 digit number with this series and the left digit of the answer is the biggest value smaller than that.

For example, the cube root of 250047 is 63: the 6 because 250 is bigger than 216 (6 cubed) but less than 343 (7 cubed); and the 3 because the last digit is 7 which is part of the 3-7 pair. The cube root of 592704 is 84: 8 because 592 is between 512 and 729; and 4 because it matches the last digit.

How about Google?

[gkwok]

Of course, as we know, the trick behind all trivial algorithms is really Google. On a whim, I just typed in

13th root of 3109483495729034820985093459038095809384834987394

and a few seconds later, I've got a new world record! Amazing! Or. . . .

impressive in someways and not in others

[Anonymous Coward]

Impressive int that the does in his head. It's not in that if your train your mind to think like that. To compare: I can do Wu style set of tai chi in roughly 5 minuts. This consits of 36 walking steps. 60 something hand moves and 20 unique kicks. I have ~1000 numbers memorised. Also not that it doesn't say anywhere in the blurb about UNIQUE numbers, if their "perfect" or not etc. While this is deffinatly a neet polor trick; and he gets kudos. My skeptic meter is off the radar, Mandle can generate unaided many complex fractions in about that time. At one point bourne could write a short shell script that fast. So what's the context of the 12 seconds?

I call skeptic.

[Anonymous Coward]

AHAHAHA this is a realy simple trick. Memorise a random digit in 22 seconds, it doesn't say ANYTHING about details. It's a kind of neumonic trick a, and b since it it doesn't say much about details who's to say that what kind of primes, what sorts of success rate. I can for a shor period of time store a 5 mile long route from here to almost anyhwere and I can memorise a numbers for a briefe period, so do many slashdotters; ip adresses, telepohone numbers, AD&D thaco scores. etc.

emulator head

[parasite]

It's obvious this guy probably just memorized the root code from a CS book, and emulated a Pentium inside of his head to run it. Not so hard you guys. sheesh.

Windows XP

[Anonymous Coward]

I don't even think the microsoft calculator can calulate the 13th root of a 100 digit number, let alone do it in under 3 hours.

But the guy can't TIE HIS SHOES !!

[Anonymous Coward]

But the guy can't TIE HIS SHOES !! Some math wiz.

Re:I can (seriously) do 43rd root of 100 digit num

[Anonymous Coward]

I wrote the parent comment as well. It seems that not many people know how to do this. I kinda assumed /. crowd would know. Maybe I should write a book on this stuff. The book would really make a very entertaining and interesting read...at least for geeks. The kind of things you can do with minimal practice will impress your girlfriend^H^H^H^H^H^H^H^H^H^H other geek friends.

Re: Possible explanation

[Glorat]

Actually, for some maths problems, it's possible to perform the entire calculation without remembering any of the numbers, thus speeding things up. A very simple but impressive feat is multiplying numbers by 11. I can multiply any large integer by 11 just about as quickly as I can read it. I don't need to remember any of the numbers.

There are similar methods for performing multiplication of large numbers and slightly harder methods for performing roots (which he may have used)

Google for trachtenberg system for more references!

I think you missed

[warrax_666]

the implied "generally". As in: It's only [generally] true for numbers which...

Re:I think you missed

[ArsenneLupin]

the implied "generally".

It only needs to be tested for numbers (N^13) mod 10 = ((N mod 10) ^ 13) mod 10.

And yes, we do have:

0^13 = 0
1^13 = 1
2^13 = 8192
3^13 = 1594323
4^13 = 67108864
5^13 = 1220703125
6^13 = 13060694016
7^13 = 96889010407
8^13 = 549755813888
9^13 = 2541865828329

Ok, so all 10 modulos match (and there are only 10 possible modulos), so how much more general do you want it?

And yes, when asserting a property about supposed to be satisfied by the members of a finite set, a proof by exhaustive enumeration is a perfectly valid proof ;-)

Yes, but...

[carnivore302]

...was he running linux?

Some numbers are easier to root than others..

[ArsenneLupin]

Hehe, just like computers... Some computers, such as Windows boxes running ASP.net an MS sequel sewer are easier to root than others, such as Linux boxen running PHP and a Mysql database ;-)

If I was him..

[leathered]

..I'd head down the nearest casino and hit the blackjack tables. Those with exceptional memories can earn much more than those who use the simpler hi/lo card counting technique.

Better article on the feat

[Peachy]

Can be found on the Times Newspaper website, includes the number itself, and the corresponding solution.

Re:I can (seriously) do 43rd root of 100 digit num

[ArsenneLupin]

Back, in my jedi-training, i was SOOOO strong in the force i could let the moon shine out of my ass!

Do you have any photo to back up that claim?

Re:Someone has to say it

[Flatline_hun]

Imagine a rings cluster of Gert MittBeowulf!!

not very usefull...but great head

[Lakedemon]

let me see..... 13th root of say 10^130 is 10^13 Wow... I just computed a 13th root of a 131 digits number in less than 2s.... Now, computing 13th root of 100 digits numbers in seconds is a nice super-power but...it's useless. It is Not one of those things that you can use often even if you are a normal mathematician. (it may be different for highly specialized ones) Besides, calculators were invented for this... Well...The good point is...if he can do that...I bet he can do a lot more usefull things with his head too. Lakedemon (phd in maths).

Re:not very usefull...but great head

[Lakedemon]

Gah...... ^_^; 13th root of say 10^130 is 10^10.... You see my point....you can have a phd in maths even if you can't compute 13th roots....

AND ANOTHER THING

[thetroll123]

How many attempts did he get? I could do this in under a second if you're prepared to overlook me getting it wrong maybe a few million times first...

this guy

[Anonymous Coward]

has two PH.D.s (psychology and pedagogy) and a master (cs)...
seems to have too much time on his hands.

Doomsday is...

[CProgrammer98]

That's easy...
Doomsday is Monday at 9:00am.... Every Monday at 9:00am... (Excpet for public holidays)

Records and Competitions

[saxonia]

Many of you have compared the ability to memorise 22 digits in 4 seconds with the time of calculating the root. Well, the point is that you do not have to read the entire number to calculate the root if you just know that it is a perfect 13th power. You can get the first digits of the result by inspecting the first digits of the power (and memorising logarithms or doing some other good estimation). And the last digits of the result can be found by inspecting just the last digits of the power.
Two more remarks:
* If someone is interested in competitive mental calculation, the mailing list at http://groups.yahoo.com/group/MentalCalculation/ is the right place for you. Last month, there was the first Mental Calculation World Cup (http://www.recordholders.org/en/events/worldcup04 / whith 17 calculators from 10 countries
* World records for mental calculation are published in "The Book of Alternative Records" (http://www.alternativerecords.co.uk/). However, because some tasks are "easier" than others, we decided to publish a record for calculating 9 tasks in a row (one power ending in 1, ..., one power ending in 9) instead of records for single tasks. (Anyway, Gert did a great job with his single task result!)

Re:I can (seriously) do 43rd root of 100 digit num

[Alsee]

Actually he was probably telling the truth. It would be fairly easy to train to find the 43rd root of a 100 digit number in under 3 seconds.

There are only about dozen perfect 43rd powers with exactly 100 digits. You only need to memorize the first 2 digits of those perfect powers to be able to spit out the right root instantly.

-

Mod Parent Down

[Anonymous Coward]

He is totally misusing Fermat's Little Theorem for a totally different purposes. Drill down a few child posts. Quit modding crrap up that is false just because it sounds like he is a math geek.

Re:Mod Parent Down

[yourmom16]

He's using Euler's Theorem, which is a generalization of Fermat's Little Theorem; Other than giving the wrong name for the theorem, what he said is correct.

That's damn impressive.

[famebait]

Let's stone him.

Geez!

[restlesscheese]

I want him on my academic team! We need a math person so badly!

Re:"memorizing 22 random digits in just four secon

[macrom]

Actually, you probably wouldn't want this guy's brain. I have no idea what this individual is like, but generally people with some sort of hyper-intelligent gift lack in other places. Sometimes they can't remember their names, how to dress themselves, when they last ate a meal, etc. I can't remember the names of the "disorders", but I remember reading about it in an introductory college Psychology text.

Autism and Asperger's Syndrome tend to exhibit these types of behaviours, I know that much.

I would wave back...

[Anonymous Coward]

... these are not the PINs you want...

Met him last week!

[rxmd]

Actually, I was quite astonished to see this on Slashdot, as I had lunch with the guy last Thursday where I work. He's nice in persion, but one of the secretaries at work said he stinks and should wash more often. I'm afraid I didn't notice it quite as badly...

He has an interesting way of getting along financially. Basically, he's living off an exclusive contract with the German TV station RTL where he's featured every now and then in shows. He also gives lectures on mathematical topics; RTL makes him charge a very steep EUR 2500 per lecture (about $3000). I think originally he studied psychology; he's still running the psychiatrist's practice in Cologne that he startet off with.

We were joking about him tackling the Millenium Problems now; I wonder if he's serious about that... but then, there's more to it than calculating in your head really fast.

There are ...

[gstoddart]

Why don't people teach this in schools? Obviously this kind of stuff is pretty tricky, but there must be other interesting little tricks and relationships that when taught correctly, could have interested a whole lot more kids in math.

I've seen a bunch of people each with their own set of these tricks. Teaching them in the normal curriculum would have the effect of utterly confusing most people.

A trick for the 13th root of a number? Well, it's cool, but I've never had occasion to take the 13th root of anything.

I had a professor once who could multiple big honking integers (ie 7-12 digits) before someone could enter them into a calculator. When he tried to explain it to me, my head damned near popped.

The understanding of these tricks often involves some really bizarre insights into the way numbers work. I think these would definitely confuse the heck out of the average student if they were confronted with them and exprected to actually use and remember them.

They might be something worth marshalling up for the math geeks to play with, but for most people they're just baggage they don't need.

Re:There are ...

[Com2Kid]

• They might be something worth marshalling up for the math geeks to play with, but for most people they're just baggage they don't need.

You know, in countries where not everyone can afford a calculator, these tricks ARE commonly taught to children.

Now compare this to my experience in school, where a teacher once told me it was impossible to calculate square roots without a calculator! (of course since then I have learned that most primary school teachers only take up to Algebra I in college so....)

Re:There are ...

[eofpi]

Okay, so quick calculation of 13th roots isn't all that practical. There are lots of fiddly little shortcuts that people discover on their own though for one thing or another.

For example, hen I was learning multiplication back in elementary school, I realized it was faster to multiply n by 10 and subtract n from the result than to multiply n by 9. It's not useful if you have a calculator around, but it's generally faster than multiplying by 9 either mentally or by hand for things past the end of your mental multiplication table. It can also be adapted to the highest single-digit value in any (whole number) base.

Re:There are ...

[Anonymous Coward]

Actually, there is a fairly well-known "trick" of sorts when it comes to multiplying by 9. Every multiple of 9 is a number whose digits will (eventually) add up to 9.

Easy examples:
9 X 7 = 63. 6 + 3 = 9.
9 X 12 = 108. 1 + 0 + 8 = 9.

Trickier example:
9 X 354.786283 = 3193.166547
Add all those numbers up (3 + 1 + 9, etc...) and you get 45. And then, 4 + 5 = 9. Just keep adding up the numbers until it is finally reduced to a single digit number -- and that single digit will always be 9.

Re:There are ...

[eofpi]

That's the shortcut to check for divisibility by 9, which itself is a special case (or a recursion, depending on how you look at it) of the divisibility check for 3 (sum the digits, and if the sum's divisible by 3, so is the original number).

What Indeed

[Torienalis]

Coming from Australia, I learnt all that you just mentioned and alot more. What I find interesting is that I learnt more World History than American Children do. It seems that for the most part American learning is almost exclusively America-Centric. That is how it seems when I talk to Americans about history. I think the assumption that non-American's find those topics to be a 'Complete Mystery' is ridiculous. I know students from Australia, New Zealand, Canada, South America, England and Holland who all learnt about that sort of thing. Not only that but we had many many Asian exchange students to my school and in many cases their Maths and English was better than ours, and they easily kept up in Physics, Biology and Chemistry. Where are these people that you mention who know nothing about these subjects?

Re:What Indeed

[Torienalis]

Oh and I just remembered that in Year 10 I had a mandatory subject called "Problem Solving and Analysis" Which was all logic puzzles and freeform learning based. So it is tought somewhere.

Re:What Indeed

[esonik]

Knowing about some subject and being able to apply the knowledge to solve a problem are two different things.

Re:"memorizing 22 random digits in just four secon

[Anonymous Coward]

Remember the movie " Rainman" with Dustin Hoffman and Tom Cruise? It was based on a true story about a man with Aspergers. Tom spills a pile of toothpicks and Dustin's character instantly states the total.

THE RECORD IS NOT OFFICIAL

[Anonymous Coward]

(http://13throot.com) The only official record for extracting the 13th root of a 100-digit number is 13.55 s. Since there is no longer an official competition in this category, the false Mittring record is worthless Nobody will publish this false record: neither 13throot.com http://13throot.com neither Alternative records Book (recordholders.org) neither Guinness Book Also the 13th root of a 100-digit number is extremely easy, in comparison with the true category for mental calculation: 13th root of a 200-digit number: http://13throot.com

Johnny Mnemonic Quote....

[Anonymous Coward]

Johnny (Keaneau Reeves): You can't shoot me.

Badguy ("Beat" Takeshi Kitano): Not...in the head.

Besides that--wearing all the body armor in the world won't protect you from a 'skullshot' by a trained sharpshooter/sniper/assassin.

If they can see your head, you can wind up dead.

As what happened to Presidents Kennedy and Lincoln.

It looks like if someone really wants you dead--make sure you have made your peace with your Maker beforehand....

But Will They Believe You?

[SeanDuggan]

The biggest catch I've found with remembering what people say is that, short of keeping a tape recorder, the person is apt to say, "No, I didn't say anything like that" and utterly believe it. There was a marvelous science-fiction story I remember reading as a kid involving a fellow who essentially had a perfect memory. It was a curse for him. When he'd correct people as to what they said, they'd insist that he was wrong. He got beat up repeatedly for settling bar bets by reciting statistics. And lastly, and probably the most incisive point the author introduced, he had the hardest time figuring out when to acknowledge meeting people. His memory meant that almost every person he passed on the street, he could remember having interacted with them in some way, but remembering how usually took him a few moments, by which time he'd either confused a complete stranger by greeting them by name, or offended someone by apparently socially cutting them. (And at that, the "unkindest cut," acknowledging their existence, then ignoring their identity)

Probably a False Claim

[changyang1230]

SO why is the claim not recognized by Guinness World Record? Must be some reason behind it besides "difficulty of standardization".

Here is one of the possibility: It is a FALSE CLAIM! Well, here is one of the link I have found. The false Mittring Claim

Well, at the end, who do you choose to believe? Your local newspaper or the Internet? I choose my intuition.