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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."

44 of 391 comments (clear)

  1. What? by HardJeans · · Score: 5, Insightful

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

    --
    "I'm not talking to myself, I'm just the only one who's listening." - Jimmies Chicken Shack
    1. Re:What? by ricotest · · Score: 4, Interesting

      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.

    2. Re:What? by jsprat · · Score: 3, Informative

      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.

    3. Re:What? by hackstraw · · Score: 4, Funny

      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

    4. Re:What? by the+angry+liberal · · Score: 3, Funny

      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.

    5. Re:What? by RichardX · · Score: 3, Informative

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

      --
      Curiosity was framed. Ignorance killed the cat.
  2. I can do better by Attar81 · · Score: 3, Funny

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

    1. Re:I can do better by NanoGator · · Score: 4, Funny

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

      "Wisconsin"

      "W."

      --
      "Derp de derp."
  3. That's nothing by bmzf · · Score: 3, Funny

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

  4. That's easy. by rackhamh · · Score: 5, Funny

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

    1. Re:That's easy. by wildsurf · · Score: 5, Informative

      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. :-)

      --
      Weeks of coding saves hours of planning.
    2. Re:That's easy. by Anonymous Coward · · Score: 3, Informative

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

    3. Re:That's easy. by stoborrobots · · Score: 4, Informative

      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.

    4. Re:That's easy. by kylemonger · · Score: 4, Informative

      (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.

  5. Family guy by comwiz56 · · Score: 4, Funny

    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

  6. Sources report... by Anonymous Coward · · Score: 5, Funny

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

  7. Re:And the answer is: by goon+america · · Score: 4, Funny

    you misspelled "forty-two".

  8. Ironic...I'm currently listening to... by taradfong · · Score: 4, Funny

    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?

    --
    Does it hurt to hear them lying? Was this the only world you had?
  9. Devi: another brilliant mathematical mind by GreenPenInc · · Score: 5, Interesting
    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. :)

  10. Re:And still has 0.00005% of getting laid by fireman+sam · · Score: 4, Funny

    I think a better joke would be.

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

    --
    it is only after a long journey that you know the strength of the horse.
  11. The first mentat? by Rai · · Score: 4, Funny

    Get this guy some sappho juice.

  12. I so call bullshit by tomstdenis · · Score: 5, Interesting

    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

    --
    Someday, I'll have a real sig.
    1. Re:I so call bullshit by kfg · · Score: 5, Insightful

      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

  13. ahh by nomadic · · Score: 5, Funny

    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.

  14. What he will be doing next week... by jmcmunn · · Score: 4, Insightful


    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.

  15. The future is here by forgetmenot · · Score: 3, Interesting

    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.

  16. Re:This is very nearly as important by CrankyFool · · Score: 3, Funny

    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.

  17. Gert disqualified and sued! by G4from128k · · Score: 4, Funny

    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.

    --
    Two wrongs don't make a right, but three lefts do.
  18. Photo of Gert Mittring here by Magickcat · · Score: 3, Informative

    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.

    --

    Si tacuisses philosophus mansisses. If you had kept quiet, you would have remained a philosopher.

  19. High pi by dexter+riley · · Score: 5, Funny

    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.

    1. Re:High pi by Nyh · · Score: 5, Interesting

      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

  20. Oh come on now. by laughingcoyote · · Score: 4, Funny

    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?

    --
    To fight the war on terror, stop being afraid.
  21. If I recall... by gravteck · · Score: 4, Interesting

    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.

  22. To how many significant figures? by jwise · · Score: 5, Interesting

    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

  23. Simpler than that by Clueless+Moron · · Score: 5, Informative
    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.

  24. method to calculate the day of the week! by GreenPenInc · · Score: 5, Funny
    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.

    1. Re:method to calculate the day of the week! by Zach+Garner · · Score: 5, Funny

      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...

  25. Re:I can (seriously) do 43rd root of 100 digit num by Smurf · · Score: 5, Informative
    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.
  26. This is not as difficult as it sounds. by e_lehman · · Score: 5, Informative

    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...

    1. Re:This is not as difficult as it sounds. by godblessthenet · · Score: 5, Funny

      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!!!!!

  27. Some of the methods used by pvg · · Score: 5, Informative

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

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

    -pvg

  28. Uh oh by dexter+riley · · Score: 4, Funny

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

  29. Roomie in College by AlexTheBeast · · Score: 5, Interesting

    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...

    1. Re:Roomie in College by SamSim · · Score: 3, Insightful

      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.