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Making Change

Roland Piquepaille writes "There are mostly four kinds of coins in circulation in the U.S: 1 cent, 5 cents, 10 cents, and 25 cents. But is it the most efficient way to give back change? This Science News article says that a computer scientist has found an answer. "For the current four-denomination system, [Jeffrey Shallit of the University of Waterloo] found that, on average, a change-maker must return 4.70 coins with every transaction. He discovered two sets of four denominations that minimize the transaction cost. The combination of 1 cent, 5 cents, 18 cents, and 25 cents requires only 3.89 coins in change per transaction, as does the combination of 1 cent, 5 cents, 18 cents, and 29 cents." He also found that change could be done more efficiently in Canada with the introduction of an 83-cent coin and in Europe with the addition of a 1.33- or 1.37-Euro coin. Check this column for more details and references." The paper (postscript) is online.

117 of 935 comments (clear)

  1. I hate math... by Swannie · · Score: 5, Funny

    I think the advantage to having a 10-cent piece is that it makes the math easy. Let's face it; can you imagine the average cashier at WalMart giving back 98 cents change with an 18-cent coin?

    Swannie

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    :q!
    1. Re:I hate math... by Anonymous Coward · · Score: 2, Funny

      Well, I can certainly imagine that. Let's see, 98 cents, that's two 40ct pieces and one 18ct piece. Easy.

    2. Re:I hate math... by Anonymous Coward · · Score: 3, Insightful

      That's part of the process that doesn't seem to have been looked at well. While the model of 'giving change' may include a number of coins, it also includes the entire process including a cashier translating the change amount into coinage, then counting it back to the customer, and much of the time, the customer counting and checking it's the right amount.

      For the pure maths side of it it's pretty neat, all the same - just not completely useful when it comes to Real World Stuff

    3. Re:I hate math... by Khasmo · · Score: 5, Insightful

      Beyond that, it also means the cashier would have to figure out what the most efficient combination of change is . . for 0.36 don't give a quater two nickels and a penny, just give two 0.18 coins.

      The logic for determining change is really easy for a cashier. start with the largest coin and work your way down until it all adds up.

    4. Re:I hate math... by Alsee · · Score: 2, Informative

      The logic for determining change is really easy for a cashier. start with the largest coin and work your way down until it all adds up.

      I can't think of an example where that doesn't work in a 1,5,10,25 system, but it is definitely not a valid rule in general. For example in a 1,40,41 system you can give 80 cents change with two coins, but your method would use fourty coins.

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    5. Re:I hate math... by Eccles · · Score: 2, Insightful

      They should just kill pennies anyway.

      Make sales and other taxes round prices up to the nearest nickel. Banks could still have rolls of pennies for those desperate for Mr. Lincoln's face, but otherwise I'd be happy to see them disappear.

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    6. Re:I hate math... by jimlintott · · Score: 3, Insightful

      When was the last time a cashier counted back your change. They usually give whatever the computer tells them. Counting back change is a lost art. There is no question that these unusual coin values would be more difficult. Ease in making change isn't simply number of coins given back.

    7. Re:I hate math... by Roto-Rooter+Man · · Score: 2, Insightful

      And nothing like fixing the typo with no editorial comment about it, so that everyone who pointed it out gets modded into oblivion.

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    8. Re:I hate math... by DarkFyre · · Score: 3, Insightful

      Yes, yes, congratulations on completing first year computer science (or math, for that matter).

      Don't you think that the current denomination systems are designed specifically so that the greedy change-making algorithm will work?

      The poster you were replying to seemed aware of that; They were merely saying that since the current denominational system has this property, it is easy to use. The problem with adding 32- and/or 18-cent coins is that the greedy approach may no longer make the most optimal change.

    9. Re:I hate math... by IpalindromeI · · Score: 3, Informative

      I can't think of an example where that doesn't work in a 1,5,10,25 system

      The reason you can't think of any examples in the 1,5,10,25 system is because 10 and 25 are both multiples of five. Therefore whatever you could make with a 25, you could also make with five 5s. So if you would ever have five 5s or two 5s, just use a 25 or a 10, respectively. In 1,40,41 system, 41 is not a multiple of 40 (or vice versa), so it makes finding the optimal number of coins a bit more difficult, since you have to find the optimal number of factors for your change given the different coins. In a 1,5,10,25 system, 5 is already a factor of the other important coins, so you can just count up how many 5s you'd need and then reduce that into 25s and 10s. (Of course the mind usually does it the other way round.)

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    10. Re:I hate math... by ukyoCE · · Score: 4, Insightful

      Close, but I dont think the multiples-of-five is the reason why it works. As someone else said, it has to do with greedy algorithms, and our coin system was specifically designed so that you'd be able to start from the biggest coin and work your way down. We went over it briefly in one of my CS courses. I think it may have been that each coin must be at least twice the value of the previous coin. Something like that.

      And as many people have mentioned, the current system is probably the best because of the ease of addition/subtraction. An 18-cent coin would be a nightmare for most minimum-wage cashiers. The only problem with our current monetary system is that inflation has made pennies freakin worthless.

    11. Re:I hate math... by jon+doh! · · Score: 2, Insightful

      The logic for determining change is really easy for a cashier

      have you ever worked at a place like walmart or target? i have. the average cashier has problems figuring out how to *scan* an item properly. what makes you think they can see .36 and figure out to give two 18cent coins? they can barely figure out the change on their own with the coins we have now. i can't tell you how many people i worked with who would round up rather than figure out how many pennies they needed to give.

      note, that's only the average ones...

    12. Re:I hate math... by Captain+Rotundo · · Score: 3, Interesting

      When I worked in retail I used to totally baffle my coworkers. They all depended on the register to tell them what to give back, then they would carefully count largest to smallest. (as they were trained) I never entered the amount the customer gave me in ther register, as it took too much time, and I would count back the change randomly (as I could/can easily figure out in my head what the best use of the coins is) I swear there were times that it seems they thought simple math was magic, and my manager thought I more than one occassion that I was doing it to steal. quite amusing.

    13. Re:I hate math... by legojenn · · Score: 2, Funny

      The 18c coin could just be a Canadian Quarter (now that the dollar is worth 72c US).

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    14. Re:I hate math... by ichimunki · · Score: 2, Insightful

      Actually, I think you meant either "40" or "forty". There is no number known as "fourty".

      The whole notion of altering the face value of coinage is a bit silly. First of all, judicious use of a 50 cent piece would make many transactions much simpler, as would actually taking advantage of the two dollar bill. I used to work in a restaurant (as both a financial manager and a cashier) where we used all available denominations under $20. Once you get into it, it's just as easy to do, and slightly faster.

      Most of this mess can be avoided by pricing things sensibly. Any price can be adjusted so that the after tax price (if tax is applicable) is a nice round number. Of course, due to rounding this sometimes breaks down on multiple item purchases, but anyone with half a brain can notice which price combinations result in bad totals and adjust the underlying prices to compensate. Or you can just take advantage of the "give a penny, take a penny" method to avoid dealing with units under five cents. You know, round in the customer's favor.

      Just be glad it's not the problem they have in Japan where a $2 item costs 240 yen and a monthly rent on an apartment can be in the hundreds of thousands. Their yen is worth less than a penny, but it's the base unit in which they count monetary value. It's like expressing every price in cents.

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    15. Re:I hate math... by e2d2 · · Score: 4, Funny

      The only problem with our current monetary system is that inflation has made pennies freakin worthless.

      Except for this penny

      Besides a good roll of pennies and a sock are good for those times you have to dish out some street therapy.

    16. Re:I hate math... by questor · · Score: 2, Funny

      It probably doesn't correspond to reality, but the topic of killing penny production came up in some episode of _The West Wing_ over a year ago, and the reason given there that it would never fly was that the chair of a committee the proposal would go through was from Indiana, Lincoln's home state...

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    17. Re:I hate math... by secolactico · · Score: 4, Interesting

      Somebody who once worked as a cashier told me that the 99 cents thing were to keep them honest.

      Usually, the customer does not have exact change to pay the $x.99 (or can't be bothered to look for pennies) and it would force the cashier to open the cash machine to give change. Upon doing this, the sale is registered and the owner will know if you pocketed the money.

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    18. Re:I hate math... by Blkdeath · · Score: 2, Insightful
      If they were doing their job correctly, they shouldn't be baffled.

      Have you been to a McDonald's recently? Them, donut shops, and any other minimum wage job tends to have a lot of "Tide me over through high school" students working for them who can't figure out change with or without a "Change due" amount in front of them.

      You seperate that number into coins using the greedy algorithm they tought you in kindergarden.

      This is making two very large assumptions;

      1. Schools taught students properly
      2. Students listened to and understood lessons

      Sadly, in many cases neither of the above conditions can be relied upon, so we get kids (and adults) who don't understand how to make regular change (ie; with a single bill of a denomination larger than the order total), letalone convenient change (ie; a 20 and a single for an 11 dollar order), and get confused and often attempt to hand back the extraneous currency.

      That is why cashiers are taught this in the first place.

      You make it sound as if there's a course. I'd go so far as to say most cashiers are taught the specifics of the cash register at hand and are left to figure things out on their own. Stores / restaurants don't tend to spend time instructing 6.85'ers what is thought to be common knowledge (how to count, how to change a $20, how to combine small coins to make the change an even amount, etc.). In the cases where such skills are taught, many teenagers exhibit stereotypical symptoms and ignore the lessons because, hey, they know it all anyways.

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    19. Re:I hate math... by mhesseltine · · Score: 2, Interesting

      My emphasis:

      The point isn't that your way is more confusing. It isn't. Some people just look at you strange because they don't see it often. The point is that the reciept says what actually happened. And the customer can then verify that he is getting the correct amount of change back without doing extra work. This is the entire point of a reciept in the first place, and the reason they train cashiers to use the greedy algorithm.

      Provided the key punching cashier monkey actually presses the right keys, yes this is true. But, how many times have you gone into a store, handed the cashier a $20 bill for example, and had them key in 2.00 <enter>, then get this confused look like "How do I get to $20 now?"

      It's probably a good idea for someone who handles cash to be able to count change without having a register tell them what it is. I've also been in a store when the power acted up, and the cashiers were powerless (no pun intended) to help anyone until the registers came up, not because they couldn't write sales reciepts, but because they couldn't count change.

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    20. Re:I hate math... by prgrmr · · Score: 2, Interesting

      and our coin system was specifically designed so that you'd be able to start from the biggest coin and work your way down

      What is it with stories like this that prompt people to make-up (or pass one made up) stuff? "Our" (i.e. the US) coinage system was not specifically designed, it was the result of a compromise:

      collectsource.com

      It is a quasi-decimal system. For it to be a true decimal system, we'd have a 20 cent piece instead of a quarter, and a 40 cent piece instead of a half dollar. The quarter was retained because for over 100 years Americans had been using 2 bit and 2 reale coins. The half dollar was actually a useful coin, a day's wages for the higher paying skilled labor jobs back in the day.

    21. Re:I hate math... by Black+Copter+Control · · Score: 2, Insightful
      Usually, the customer does not have exact change to pay the $x.99 (or can't be bothered to look for pennies)

      That doesn't take into account taxes which almost always mess up the totals. Besides.. If you're going to be dishonest, then why not just keep a cache of pennies on top of the till?

      The actual answer is apparently marketing: They definitely do studies on these things.
      $4.99 is less than $5.00. The fact that it's only infinessimally smaller doesn't quite register on the harried consumer's mind. People seem to think in round things to the nearest 5, because
      $4.97 will often seem like more than $4.99. I'm guessing that it's internally converted to more than $4.95.
      $*98 is generally almost as good as *99, bur it seems to make some people stop and think.
      Similarly *95 works as good as *99. I'm guessing that it works because it's one 'chunk' down (the chunk being $.05, now rather than $.01). My guess as to the reason why *.99 is used more more often than *.95 is that $.04/unit adds up over a million boxes without adding enough sales to make it worthwhile.

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  2. Yeah Right... by IpsissimusMarr · · Score: 5, Funny

    Are you kidding me?!

    Have you ever gotten a bill for dinner for say $12.50 and you give the cashier $15 saying the tip is included?
    You would think 15.00 - 12.50 is doable right?

    HELL NO! The cashier pulls out a calculator to do the math so she can write it in for the waiter's tips!!!

    If people can't add things like this 18cent coins are out of the question.


    Although I would like to hear a cashier go,
    "That makes $0.88 change sir." Pick out two quarters then, ... *pause* .... and just stare blankly at the change drawer.

    --
    "Engineers do the work of man, Physicists do the work of God"
    1. Re:Yeah Right... by ip_vjl · · Score: 5, Funny

      One time at a grocery/conveneience store, I had a total come to something like $1.87

      Wanting to minimize some of the change in my pocket, I gave the clerk $2.00 in bills and 12 cents.

      The clerk tried to hand it back, saying "it's only $1.87"

      I said, "yes, but this way, I'll get a quarter back in change."

      He took the money, punched it into the cash register, and as he handed me back the quarter, he said "How did you know that?"

      It's funny (in a VERY sad way) that to him, the cash register was this magic oracle that told him what to do, and that it didn't occur to him that what he was doing was even knowable without its use.

    2. Re:Yeah Right... by Alsee · · Score: 2, Insightful

      America has $1 and 50 cent coins, but they are kinda rare.

      -

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    3. Re:Yeah Right... by gentgeen · · Score: 5, Insightful

      It's funny (in a VERY sad way) that to him, the cash register was this magic oracle that told him what to do, and that it didn't occur to him that what he was doing was even knowable without its use.

      I am a High School math teacher, and I can't agree with this statement enough. Somedays I laugh, somedays I cry, but it is always sad when I see a student need the calculator for the most BASIC of operations (And I am not even counting the OP's example as "basic", that would be "basic+")

      I think it all comes from the fact that students are allowed to use calculators at such an earlier point in thier schooling. I am only 29, but I was not allowed to use a calculator in school until somewhere around 11th grade. It really hones (sp?) those basic math skills. I'll step off my soap-box now Sorry ;-}

    4. Re:Yeah Right... by HogGeek · · Score: 2, Funny

      Take the coins, your missing out on watching the dancer try to pick it up with her ...

    5. Re:Yeah Right... by ip_vjl · · Score: 5, Insightful

      I don't blame people for not being able to do math in their head. I know some smart people that have trouble doing calculations without paper. My wife was a math major in college, and she sometimes has problems doing calculations in her head.

      The thing that struck me about this guy was that it wasn't even that he couldn't do the math in his head ... he wasn't even aware that there was something that he could do to arrive at the answer. It's as if he didn't know that math even existed.

    6. Re:Yeah Right... by TopShelf · · Score: 2, Insightful

      The real problem is that too many people look down on people in those jobs. There's absolutely no reason why somebody can't take pride in their work, no matter what they do. Well, maybe not spammers, but otherwise...

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    7. Re:Yeah Right... by MCZapf · · Score: 2, Insightful

      But using a dollar coin in a vending machine is a dream compared to coaxing the machine to take a dollar bill. The only problem is that a lot of older machines don't take dollar coins.

  3. D'oh! by aitala · · Score: 3, Funny

    Is it too early in the morning or does this article not make sense? I have never seen an 18 cent piece in circulation n the US...

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    1. Re:D'oh! by Trailer+Trash · · Score: 4, Funny

      Is it too early in the morning or does this article not make sense? I have never seen an 18 cent piece in circulation n the US...

      I'm waiting to see if Taco screws it up in the dup tomorrow, too...

      MDC

    2. Re:D'oh! by crazyphilman · · Score: 3, Funny

      I think you can file this article in the "most useless use of research resources ever" category. Whoever this Waterloo guy is, he REEEEALLLY needs to get a new hobby.

      18 cent coins? 4.70 coins per transaction? Give me a break. I was a geek growing up and even *I* feel like smacking this guy.

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  4. Instead... by frodo+from+middle+ea · · Score: 5, Insightful

    Why not just get rid of silly prices like 99.99 and 4.37 and 1.49. ?
    Why not round prices to dimes ? Or even quarters ?

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    1. Re:Instead... by Bazman · · Score: 2, Insightful

      Because retailers would round _upwards_.

    2. Re:Instead... by xyzzy · · Score: 3, Insightful

      Fine, who cares, let them! For god's sake, they're fooling no one. In addition, they should incorporate sales tax INTO the price so that the price you see is the price you pay. If an article is $4, it's $4! No change necessary!

    3. Re:Instead... by jmv · · Score: 5, Informative

      In France (and probably other countries) most of the prices end in .00 and the taxes are already included (unlike Canada where I live). It's much simpler that way. If only there was a way to convince stores to do that in here...

    4. Re:Instead... by aborchers · · Score: 3, Funny

      So getting rid of marketeers would *also* simplify making change? What are we waiting for?!

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    5. Re:Instead... by bwalling · · Score: 2, Insightful

      Marketeers consider those prices psychologically important

      Those prices have been proven to influence buyers. They won't go away until people quit acting like idiots.

    6. Re:Instead... by sehryan · · Score: 3, Insightful

      That would increase costs to the company. Take a department store. They can mass produce a sign for a certain item without any worries. Because sales tax can be different all the way to the county level, the company now has to make signs for every variation of price.

      I suppose they could just print out signs with an average price, and take a hit in certain areas, and make a much larger profit margin in others. It might balance out in some areas, but possibly not in others. And if you are a consumer in one of those higher profit margin areas, then you are getting screwed as well. It would work, but I don't think anyone would be too terribly happy with it

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    7. Re:Instead... by pi+radians · · Score: 3, Informative

      If only there was a way to convince stores to do that in here...

      Its not up to the store, but the law. You must show the PST and GST on every sale in Canada. There was some debate a couple years ago about changing it to hidden costs, but that seems to have been quelled with recent wars and weed laws.

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    8. Re:Instead... by RaboKrabekian · · Score: 2, Insightful

      For god's sake, they're fooling no one.

      Who are you kidding? Of COURSE they're fooling someone. It's a proven fact that a given good will sell more units at $9.99 than at $10.00. YOU may not think you're being affected, but the truth it is works. Retailers price their goods at a level that will maximise sales.

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    9. Re:Instead... by GospelHead821 · · Score: 5, Insightful

      They're not trying to fool anybody. At least, that was not the original intent of setting prices at $9.99 instead of $10.00. It was a technique that was intended to help keep cashiers honest. If an item cost exactly $10.00, the cashier didn't need to open the drawer to get change for the customer. At some point, it was determined that cashiers who did not have to open the drawer were statistically more likely to pocket the money themselves than to put it in the register. So prices were dropped by a penny to force the cashier to open up the cash drawer, to get change for the customer, thus increasing the statistical likelihood that company gets its money.

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    10. Re:Instead... by Erik+Hensema · · Score: 2, Interesting

      In the netherlands (and most, if not all, of europe), consumer prices must always be advertised including VAT. This includes pricetags in the store itself and commercials on TV and such. It is illegal to advertise prices without VAT to consumers.

      Consumers never have to deal with prices without VAT included. The price isn't even mentionned anywhere.

      Because VAT is tax deductable when you buy a product for commercial use, you can get a receipt which shows how many VAT you have paid.

      It actually never occured to me that this would be different in other countries. It makes absolutely no sense to me ;-)

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    11. Re:Instead... by Phreakiture · · Score: 2, Informative

      Don't you think that the addition of sales tax already solves this problem?

      On untaxed items (e.g. Groceries here in New York State) your explanation makes sense, but on most items we pay a sales tax somewhere between 4 and 9 percent, depending on the county and item. It almost always requires change.

      Further, if your explanation were the correct one, then gasoline would not be priced such that it is always something and 9 mils (e.g. $1.529).

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    12. Re:Instead... by xyzzy · · Score: 2, Informative

      I'm really sorry to say that your last sentence exactly encapsulates the US buying experience :-(. For your hypothetical $3.99 item, the price can be $4.19 (5% tax rate), $4.21 (5.5% tax rate), or ghod knows what -- sales tax in the US ranges from 0% to 8-9%, and sometimes you have state and local tax. It's really a P.I.T.A. (pain in the ass).

    13. Re:Instead... by ortholattice · · Score: 2, Interesting
      Fine, who cares, let them! For god's sake, they're fooling no one. In addition, they should incorporate sales tax INTO the price so that the price you see is the price you pay. If an article is $4, it's $4! No change necessary!

      Give it up, you will never ever see logical pricing that doesn't require loose change.

      $19.99 may not fool you or me, but subliminally many people perceive it quite differently from $20. It begins with a "1". "In the teens" seems easier to justify psychologically than $20 for an impulse buy. Everyone knows about the trick but it still works in spite of that. It's very obvious but at the same time very subtle, and it works because most people think with their emotions rather than logic. Marketeers know this, and we will see this trick done until the end of time. And then there are gasoline prices - I don't recall ever seeing one that didn't end in 9/10 of a penny.

      Curiously, another pricing trick that is done in some cases - especially "wholesale" or "factory outlet" type places - is to do the opposite - price it at some oddball amount _other_ than $19.99, like $18.54 or $21.43. This appeals to bargain-hunters who are looking for "deals" and are suspicious of the .99 trick. An oddball price can give them the psychological impression that the vendor is cutting the price to the bone, down to the last penny they can trim.

      Yet another ploy, that works with rich people buying luxury items, is to purposely price something with round numbers. You don't often see a painting in an art gallery, or a high-fashion designer dress, priced at $2399.99 - it would almost make it seem "cheap" to some of these people. A round number like $2400 makes it seem more sophisticated, and nitpicking about price or using cheap pricing tricks is beneath these people.

      "Taxes not included" is done to make things seem cheaper and more competitive, again a subtle psychological trick to get the customer to cross that fragile threshold of deciding to purchase while maximizing their profits. Once at the cash register, when the real amount hits home, that borderline psychological decision has already been made and the customer is now emotionally committed to the purchase. And the listed price is going to be $19.99 anyway, whether it cost the vendor $10 or $12, taxes included or not, so why should the vendor forfeit the extra tax money?

      And then there are those "deals" in TV ads or web sites that seem cheap until they add in the shipping and "handling" charge. That's a whole discussion in itself.

      There is one thing I've always wondered about - taxes are always including for certain items like gasoline, alcohol, or cigarettes. In Massachusetts I recall it is or used to be $.47 per gallon. So I wonder why gas stations don't advertise "$1.09 9/10 plus tax" instead of "$1.56 9/10". Is there a law prohibiting this or something? I would almost like to see it done this way because it would make people painfully aware of the money they're paying to the government.

    14. Re:Instead... by simong_oz · · Score: 4, Informative

      In Australia copper coins (1c & 2c) were taken out of circulation in 1991 (I think). So everything is rounded to a multiple of 5c. The rules for the rounding (set out by law) are:

      For cash transactions:
      1 & 2 cents -- rounded DOWN to the nearest 10 cents
      3 & 4 cents -- rounded UP to the nearest 5 cents
      6 & 7 cents -- rounded DOWN to the nearest 5 cents
      8 & 9 cents -- rounded UP to the nearest 10 cents
      Rounding is on the total value of the bill. Individual items should never be rounded.

      And where a consumer pays by cheque, credit card or EFTPOS (electronic transaction) there is no need to round at all.

      So basically you win some and you lose some, but it evens out in the end. If you're really diligent, yes you can use it to your advantage, but most people have a life instead.

      --
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    15. Re:Instead... by ManxStef · · Score: 2, Interesting
      I think it also had something to do with the way a transaction works at your average store.

      Consider the following typical purchase:
      • You walk into the store.
      • You find yourself a bag of CheesyPoofs, which cost $0.99USD (hey, they're that expensive thanks to the constant free advertising the get on SouthPark!), and head over to the counter.
      • The cashier looks up from their magazine (sneers) then rings up the price on the till, and asks for 99 cents.
      • You hand over a dollar, and grab your bag of CheesyPoofs
      • The cashier opens the register, puts the dollar in, grabs a cent and hands it to you, then says, "Have a nice day!" (sarcastically)
      • You then leave the store
      Now think how different this'd be if everything matched the common notes. You'd hand over a dollar, but then as you've paid in full you've got no reason to hang around anymore so might just walk out with the goods. This kinda 'breaks' the transaction - you may've made a mistake and under or overpaid, or maybe you have something in your hands which you forgot to pay for, but the cashier can't correct this 'cause you've already left. Equally, they don't get to check you out, or say "Have a nice day!", which, as much as people hate it, is a typical part of customer service/interaction and may encourage you to shop at the same store again ('cause that cute chick behind the counter smiled at you as she gave you your change). It's also a signal that the transaction is complete and you can leave.

      So, without having to wait for some token amount of change, an essential part of completing a monetary transaction is removed, and things become a lot more difficult. I think *that* is why prices are always XX.99 (as well as the obvious marketing "looks cheaper" aspect).
    16. Re:Instead... by totallygeek · · Score: 2, Insightful
      $19.99 may not fool you or me, but subliminally many people perceive it quite differently from $20.


      Du Pont also has a posted speed limit of 19 instead of 20 on their plants for several reasons. One of the top reasons being that at 20, a majority of people will drive any speed in the 20's. At 19, amazingly, they will not drive above 20.


      People familiar with Du Pont will also remind me that 19 sticks in your head better than 20 because it is an odd number to see on a limit sign -- so you will adhere to it because you are more concious about it.


      What I find interesting, though, are the people that think the .9 cents is the tax on gasoline! When I see a sign at a fill-up station, and it says 1.299 per gallon, I say gas is going for 1.30. And, I know that here in Texas, 38.4 cents is the tax per gallon!

  5. Re:Forget it. by Ripplet · · Score: 2, Funny

    Exactly. All you need is a 1 cent coin, and a, er, zero cent coin!

    --

    Skiing? Check out The Independant Skiers Portal

  6. Ah the new math. by SphynxSR · · Score: 2, Funny

    I had 18 cents everytime I heard that.

    --

    I don't suffer from insanity, I enjoy every minute of it.
  7. The quarter is hard enough by charlieo88 · · Score: 5, Funny

    I was at a conveinece store yesterday. The price came to $1.37. I tendered $2.12. The cashier's head almost exploded.

    1. Re:The quarter is hard enough by LPetrazickis · · Score: 3, Funny

      As someone who used to work in a similar establishment, let me just say that I hated people like you.;)

      And I like math.:P

      --
      Is this a sigs-optional kind of place? 'Cause I am totally down with that if you know what I mean.
    2. Re:The quarter is hard enough by asmithmd1 · · Score: 4, Funny

      Here is a true story about someone who almost got arrested for trying to buy a burrito with a $2 bill. A mall security guard actually helped out.

    3. Re:The quarter is hard enough by Anonymous Coward · · Score: 2, Insightful

      When working as a cashier at a grocery store, I had pretty much memorized a mental table of 100's-complements(which actually breaks down into two tables of 10's-complements and 9's(tens digit)-complements). I could tell you within milliseconds that 2.00-1.37=0.63. I could look at you and do the mental math for a couple of seconds to tell you that 2.12-1.37=0.75.

      Wanna see those tables? Here you go.

      tens digit:
      -------------------
      9 - 0
      8 - 1
      7 - 2
      6 - 3
      5 - 4

      ones digit:
      -------------------
      9 - 1
      8 - 2
      7 - 3
      6 - 4
      5 - 5
      0 - 0

      It's very simple math. Most likely, that blank stare you get from the cashier is your own damn fault for making it more complex. Then again, there are a lot of clueless cashiers out there... Maybe I'm just a change-giving genius. :D

  8. Yeah, right... by Frightened_Turtle · · Score: 5, Funny

    So- you have 7 18-cent coins, Susie gives you 13, and you give Bobbie 3. How many nickels must Daddy give you for your 18-cent coins...?

    Then, you get on a train in Boston traveling east at 300 MPH. In 30 minutes, will you really care about how many 18-cent coins you're carrying?

    --


    Whew! This water sure is cold!
    1. Re:Yeah, right... by d_lesage · · Score: 2, Funny

      If you get on a trin travelling *east* from *Boston*, it's going to take you a hell of a lot less than 30 minutes not to care. You're more likely to care about the lack of oxygen.

      --

      Ich werde nie wieder denken
  9. Science v. Common Sense by MilesParker · · Score: 5, Interesting

    More proof of the ungoing schism between science and common sense.

    Me, I'm on the side of science.

  10. More to transactions than number of coins. by Violet+Null · · Score: 3, Insightful

    You think it's bad enough when the cashier has to use the machine to figure out how much change to give, and in what denominations? You think it's bad when the little old lady in front of you in line starts counting, and then double-counting to make sure, the change she's going to hand over?

    You give them a 29 cent piece and see how fast things get.

    I'm willing to bet that most of the "coin cost" or whatever you want to call it comes from pennies, anyway -- if the dollar amounts are random, every 5 transactions are going to involve (0 + 1 + 2 + 3 + 4 = ) 10 pennies, or 2 pennies per transaction. Rounding prices to the nickel would be simpler, easier, and more efficient.

  11. Actually, i think it started to help prevent by Unknown+Poltroon · · Score: 3, Insightful

    employee theft.
    If the price is 1.00$, the person working the regster can just take the buck, or five, or whatever, and slide it into their pocket. If its .99, or 1.95, or 7.53, they gotta make change by opening the register.

    --
    All Troll + "offtopic" mods are meta moderated as "Unfair", because you abused the system.
  12. typical Computer Science logic by citroidSD · · Score: 2, Insightful

    more efficient transaction costs?? Again the computer scientists are concentrating on the efficiency of the system, without any regard to the efficiency of the user. What is more important, handing back a smaller amount of change, or allowing for quicker mental computation of what coins to use in the transaction? For example when you are told something costs $3.48, it takes more time to calculate how to break up 48 cents into the available coin denominations, then it does to to actually exchange and identify the coins. The system is not what needs to be optimized, instead the user is what matters, and our mind work well in 10's and 5's.

  13. Oh, that'll work well by Viogression · · Score: 4, Interesting

    My mother went to the store to purchase something. The price on it was $20. It was also marked 25% off. It rang up as $18 instead of $15. My mother pointed this out, but the cashier would have none of it. "No, no, that sounds like 25% off."

    How the hell can we expect these people to handle 18 cent pieces when they can't even figure out what 25% of 20 is?

  14. Or, even better ... by simong_oz · · Score: 2, Informative

    Do what Australia did a while back and round everything to the nearest 5c and get rid of 1c and 2c coins entirely (so now Australian coins are 5c, 10c, 20c, 50c, $1 and $2). I couldn't decide whether I liked it to start with, but after a little while you realise just how much shrapnel you carry around and have no intention of using except to empty it from your pocket/wallet at the end of every day. Every time I go to another country and have to again deal with 1/2 cent/euro cent/pence/etc I just appreciate this move even more.

    --
    "Because it's there." - George Mallory, when asked why he wanted to climb Mt Everest, March 18, 1923 (New York Times)
    1. Re:Or, even better ... by simong_oz · · Score: 3, Informative

      the rounding is only on the final payment at the till, not on individual items. And it's only for cash transactions, not electronic transactions. Sometimes it rounds in your favour, sometimes in the store's favour, but it evens out in the end. Yes, it can be manipulated to save you a cent or two here and there, but anyone doing that should probably worry about getting a life first.

      --
      "Because it's there." - George Mallory, when asked why he wanted to climb Mt Everest, March 18, 1923 (New York Times)
  15. Minimize coins in pocket by f97tosc · · Score: 3, Interesting

    It seems like the objective here was to minimize coin exchange. Ususally I try to minimize the number of coins in my pocket.

    If something costs 77c I give them 1.02 - and get a quarter back. In the US, the tellers stare at me blankly, but then dutifylly enter the amount I give them - and then smile in amazement at the simplicity of the exchange.

    In Japan, it is almost the other way around. The tellers come up with the most creative combinations that minimize my number of coins (and maximize theirs - this is in both of our interest).

    Tor

    1. Re:Minimize coins in pocket by Obiwan+Kenobi · · Score: 2, Informative

      The tellers come up with the most creative combinations that minimize my number of coins (and maximize theirs - this is in both of our interest).

      Just as a note here, its probably not in their best interest to get back as many coins as possible.

      I used to admin at a bank, and you are charged for "coin." This means the more you bring in which is unsorted, the more you are charged.

      Of course, if they roll their coin then this is not a problem.

      However, it would cost them more if they try to maximize their coin input without rolling.

      Also, this is probably the most nit-picky post in my history of posting. God help us all.

  16. This is why Human Interface Design is important by Bingo+Foo · · Score: 3, Insightful
    1. Some egghead thinks "optimal" means "fewest coins returned in change, on average."
    2. He recommends introducing 18 and 83 cent coins.
    3. The people who actually use coins laugh at this idiocy.
    Sheesh, "optimal" coinage denominations are those that make using coins easiest. That means quick mental calculations of change, manipulating them with your fingers, and passing them back and forth.

    The ivory tower academics are certainly earning their reputation for foolishness.

    --
    taken! (by Davidleeroth) Thanks Bingo Foo!
    1. Re:This is why Human Interface Design is important by omega_cubed · · Score: 4, Informative

      Some egghead thinks "optimal" means "fewest coins returned in change, on average."

      No no no. Academia don't have to think about definitions. We just define it that way.

      Be seriously, RTFA, people. The important part of this result is not that 18 or 83 cent recommendations. The author did it in jest in reference to the phrase "What this country needs is a good five cent cigar". (cited in the footnote of the paper). Just wait for /. to come along and rip everything out of context.

      The important part of this paper is the second half, the general analysis of methods for finding "optimal" denominations or "optimal" change returns (the first defined to minimize the number of coins returned on average, the second defined as given a set denomination, finding the best way to represent a given amount). It gives asymtotic results. It is more of a computer science excercise then anything else.

      W

      --
      Engineers also speak PDE, only in a different dialect.
    2. Re:This is why Human Interface Design is important by dave_mcmillen · · Score: 4, Insightful

      There's another problem. Quote from the ScienceNews article:

      Assuming that each amount of change between 0 and 499 cents is equally likely, Shallit's calculations show that the average cost of making change would fall from 5.90 to 4.58 coins per transaction with the addition of an 83-cent coin.

      That's a pretty big assumption, isn't it? I'd assume that amounts of change would cluster around certain values. That was one thing that caught my interest, so I went to look at the article to find out how they evaluated that effect. Answer: apparently they didn't.

      To be fair, it's quite possible -- even probable -- that the original article was a light-hearted, tongue-in-cheek sort of piece, and that the author has been horrified to see it turned into a serious suggestion about actually changing the denominations of coins.

      In fact, the more I think about it, the more likely this seems. From TMI's site: "The Mathematical Intelligencer encourages authors to write in a relaxed, expository style and to include pictures and other graphics with articles. Opinion, mathematics, and historical comments can (and often should) be intermingled to make lively reading. Humor and controversy are welcome." So it was probably just a goofy abstract problem, written for entertainment value, not "serious" research. So I take it all back: let's give the guy a break, smile quietly, and move on.

  17. Worst.... idea.....ever........ by Dr.+Mojura · · Score: 2, Interesting

    Any gain in efficiency of number of coins returned is going to be substantially offset by the decrease in efficiency of time required for people to calculate the change. Seriously, the simplest solution is to do away with the penny and round up/down to the nearest nickel.

    --
    "Nothing exists except atoms and empty space; everything else is opinion." - Democritus
  18. 18, it's a magic number. by MexicanMenace · · Score: 5, Funny

    Don't y'all remember the SchoolHouse Rock about counting by 18?

    *taps foot*

    Eighteen is a magic number.
    Yes it is, it's a magic number.
    Somewhere in the ancient, mystic eighteenity
    You get eighteen as a magic number.
    The past and the present and the future,
    Faith and hope and charity,
    The heart and the brain and the body
    Give you eighteen.
    That's a magic number.

    18, 36, 54 . . .
    72, 90, 108 . . .
    126, 144, 162 . . .
    180.

    1. Re:18, it's a magic number. by muon1183 · · Score: 2, Informative

      Regarding the ancient, mystic aspect of your post, I think I can explain the history behind this some. In the old hebrew counting system, the leters were used for numbers (but it was decimal, it's just that they used letters instead of the current notation), and the letters for 18 spelled out the word for life. Hence, 18 was (and still is by some people) considered lucky.

      --

      There's no sig like SIGSEG
  19. Preposterous by syle · · Score: 5, Funny
    An 18 cent coin is a good idea, but it's only a start. What we really need is one coin per possible amount of change. That way, when you pay with $1.00 for a $0.63 candy bar, you just get one 37-cent coin in return.

    This approach simplifies all transactions to one-coin change. Some people might argue that this is just too many coins to keep track of, but since no one keeps track of their change anyway, it wouldn't matter. It's easier to use the new change to pay as well: Instead of $0.67 being 2 quarters, a dime, a nickel, and 2 pennies, it can be paid in one coin. Or, you could use a 50-cent and a 17-cent piece. Or two 27s and a 13! The possibilities are endlessly easy!

    Some people say that it's a problem to differentiate the 99 different coins (95 new coins) by sight. There's a simple answer to this -- each coin would have a number of sides based on its amount. A 4-cent coin is a square, an 8-cent is an octogon, and so forth. So, remember, don't give them three quarters -- just reach into your pocket, feel for the coin with 75 sides, and hand it over.

    Oh, and if you can't tell a 99-sided coin from a 97-sided coin by sight, perhaps you should stick to smaller denominations.

    The new two-cent coins are easy to lose, so be careful.

    --

    /syle

    1. Re:Preposterous by brer_rabbit · · Score: 4, Funny
      I hope you're joking about having 99 different-shaped objects in your pocket.

      I believe he was joking about having 99 different coins. An ideal solution would be to have 100 different coins, and include a zero or "null" coin. Therefore the protocol for every transaction could expect a coin.

  20. Re:4 coins? by Tumbleweed · · Score: 2, Funny

    > Have I been living under a rock? Are my dimes now worth 18 cents?

    Apparently so. That's what your dollars are now worth. :)

  21. why did we ... by da5idnetlimit.com · · Score: 5, Interesting

    Why did we fight against the Imperial System ?

    easy, look :

    Measures of length
    After 1959, the U.S. and the British inch were defined identically for scientific work and were identical in commercial usage (however, the U.S. retained the slightly different survey inch for specialized surveying purposes). A similar situation existed for the U.S. and the British mass unit pound, and many relationships, such as 12 inches = 1 foot, 3 feet = 1 yard, and 1760 yards = 1 international mile, were the same in both countries; but there were some very important differences.

    Measures of volume
    In the first place, the U.S. customary bushel and the U.S. gallon, and their subdivisions differed from the corresponding British Imperial units. Also the British ton is 2240 pounds, whereas the ton generally used in the United States is the short ton of 2000 pounds. The American colonists adopted the English wine gallon of 231 cubic inches. The English of that period used this wine gallon and they also had another gallon, the ale gallon of 282 cubic inches. In 1824, the British abandoned these two gallons when they adopted the British Imperial gallon, which they defined as the volume of 10 pounds of water, at a temperature of 62F, which, by calculation, is equivalent to 277.42 cubic inches. At the same time, they redefined the bushel as 8 gallons.

    In the customary British system the units of dry measure are the same as those of liquid measure. In the United States these two are not the same, the gallon and its subdivisions are used in the measurement of liquids; the bushel, with its subdivisions, is used in the measurement of certain dry commodities. The U.S. gallon is divided into four liquid quarts and the U.S. bushel into 32 dry quarts. All the units of capacity or volume mentioned thus far are larger in the customary British system than in the U.S. system. But the British fluid ounce is smaller than the U.S. fluid ounce, because the British quart is divided into 40 fluid ounces whereas the U.S. quart is divided into 32 fluid ounces.

    From this we see that in the customary British system an avoirdupois ounce of water at 62F has a volume of one fluid ounce, because 10 pounds is equivalent to 160 avoirdupois ounces, and 1 gallon is equivalent to 4 quarts, or 160 fluid ounces. This convenient relation does not exist in the U.S. system because a U.S. gallon of water at 62F weighs about 8 1/3 pounds, or 133 1/3 avoirdupois ounces, and the U.S. gallon is equivalent to 4 x 32, or 128 fluid ounces.

    1 U.S. fluid ounce = 1.041 British fluid ounces
    1 British fluid ounce = 0.961 U.S. fluid ounce
    1 U.S. gallon = 0.833 British Imperial gallon
    1 British Imperial gallon = 1.201 U.S. gallons

    Measures of weight and mass
    Among other differences between the customary British and the United States measurement systems, we should note that they abolished the use of the troy pound in England January 6, 1879, they retained only the troy ounce and its subdivisions, whereas the troy pound is still legal in the United States, although it is not now greatly used. We can mention again the common use, for body weight, in England of the stone of 14 pounds, this being a unit now unused in the United States, although its influence was shown in the practice until World War II of selling flour by the barrel of 196 pounds (14 stone). In the apothecary system of liquid measure the British add a unit, the fluid scruple, equal to one third of a fluid drachm (spelled dram in the United States) between their minim and their fluid drachm.

    In Great Britain, the yard, the avoirdupois pound, the troy pound, and the apothecaries pound are identical with the units of the same names used in the United States. The tables of British linear measure, troy mass, and apothecaries mass are the same as the corresponding United States tables, except for the British spelling "drachm" in the table of apothecaries mass. The table of British avoirdupois mass is the same as the United States table up to 1

    --
    It takes 40+ muscles to frown, but only four to extend your arm and bitchslap the motherfucker
  22. Bad Assumption by SuperHighImpact · · Score: 2, Insightful
    Shallit assumed that every amount of change between 0 and 99 cents is equally likely.

    I understand that an assumption like this is necessary to even begin an anaylysis using our western logic system, but this assumption makes the study useless.

    There's no way that the distibution curve is flat. People spend a lot of time and money price setting as described here and you better believe they know how to price their goods to maximize profit.

    This study also doesn't take into account people like me, who make a game out of minimizing the number of coins in my wallet/pocket. If I can prevent getting 94 cents in change by carrying and relinquishing a penny and a nickle, I'll do it.

    --
    sHi
  23. Get rid of 1c pieces! by Chmarr · · Score: 2, Insightful

    One can reduce the amount of change simply by getting rid of the silly 1c piece, like Australia did (it got rid of both 1c and 2c pieces).

    Sure, people will bitch and moan for about 6 months, but then noone would ever consider going back.

    All you need to do is 2/3 round at the till. It's great! :)

  24. Re:A $0.18 coin? by Art_Vandelai · · Score: 2, Funny

    A Canadian quarter is worth about 18 cents. Just use those.

  25. Bad Assumption by isoga · · Score: 2, Insightful
    It's a fun idea but flawed - Shallit assumed that every amount of change between 0 and 99 cents is equally likely.

    Is obviously not true - prices are clustered at certain points, eg 95c or 99c, so the typical amount of change would be skewed as well. Would be nice to see the experiment using real data for typical prices.

    Also, I wonder to what extent the demoninations of currency in use effect the prices of goods?

    dave

    ===== Tech, Ramblings, Photos --> davidgoodwin.net

  26. Bring back LSD by freddled · · Score: 2, Interesting

    No not that LSD I mean good old pounds shillings and pence. There you have a system which evolved - it sounds to me - to do precisely this. Whats more, even uneducated victorian urchins understood what two guineas less half a crown tuppence ha'penny was and could offer you change in the form of shillings, florins, pennies, etc.


    For those who don't know what I'm talking about, British currency up to the 1970s was counted in pennies, shillings (12 pennies), twenty of those to a pound, with a guinea at 21 shillings (lend a pound, get a guinea back in a year, see, works for interest too).

  27. Semi-Log; Diameter; Thickness; Mass by 4of12 · · Score: 3, Interesting

    Euro 1,2,5,10,

    When I was in Europe recently I noticed their semi-log scale change system of 1,2,5,10,20,50,... and really liked it compared with the US system, which has quarter dollars, but not $2.50 bills.

    Evidently two bits are indivisible anyway these days, so Americans don't seem inordinately hooked on using powers of 2 to divide up their money all the time.

    The US should have its monetary system go the same direction as the stockmarket which recently abolished fractions (down to what, 1/64, 1/128?) in favor of decimal stock prices.

    Also, the US treasury needs to push $1 coins (and perhaps $2 and $5 coins) because the paper money wears out so much faster and costs more to replace than coinage.

    And, while we're on the subject of monetary redesign, coins should be monotonically increasing in diameter, thickness, and mass to make it easier for people with poor vision.

    In fact, if the weights were done nicely, it might even be possible to start weighing heterogeneous buckets of coins to obtain value (assuming no rocks, counterfeits).

    Or to measure linear thickness of heterogeneous coin stacks and still have $/inch be as good a measure as $/weight, again, to avoid explicit counting.

    Ahh, if nerds were running the world, things would be so damn efficient...

    --
    "Provided by the management for your protection."
  28. Am I retarded? by medscaper · · Score: 4, Funny
    The price came to $1.37. I tendered $2.12.

    Uhhh...did anyone else have to use a calculator or pencil for this one and go, "Oh, I get it. Those idiot cashiers."?

    ...snicker...

    --
    Any sufficiently well-organized Government is indistinguishable from bullshit.
    1. Re:Am I retarded? by rnelsonee · · Score: 2, Funny

      Nope, only cause I read the earlier post about $1.87, and tendering $2.12. I realized "hey, this guy is getting three quarters back cause the other guy that commented got one back!" :)

  29. Re:Forget it. by omega_cubed · · Score: 5, Informative
    Quoth Terry Pratchett and/or Neil Gaimen (as they coauthored, and I have no idea which came up with this) in Good Omens:
    NOTE FOR YOUNG PEOPLE AND AMERICANS: One shilling = Five Pee. It helps to understand the antique finances of the Witchfinder Army if you know the original British monetary system:

    Two farthings = One Ha'penny. Two ha'pennies = One Penny. Three pennies = A Thrupenny Bit. Two Thrupences = A Sixpence. Two Sixpences = One Shilling, or Bob. Two Bob = A Florin. One Florin and one Sixpence = Half a Crown. Four Half Crowns = Ten Bob Note. Two Ten Bob Notes = One Pound (or 240 pennies). One Pound and One Shilling = One Guinea.

    The British resisted decimalized currency for a long time because they thought it was too complicated.
    --
    Engineers also speak PDE, only in a different dialect.
  30. Re:Canadiana by canowhoopass.com · · Score: 3, Informative

    > In Canada, it's illegal to pay for any good or service, with more than 25 of any given denomination.

    What he's talking about can be found in Section 8 of the Currency Act.

    Basically it is a no-nuisance law to stop people from doing things like pay fines using pennies. It doesn't say the money can be confiscated...

    Many businesses will still except coins if they have been rolled. I know I have paid for movie tickes and extra value meals with rolls of nickles and dimes.

    From the statute:

    (2) A payment in coins referred to in subsection (1) is a legal tender for no more than the following amounts for the following denominations of coins:

    1. forty dollars if the denomination is two dollars or greater but does not exceed ten dollars;
    2. twenty-five dollars if the denomination is one dollar;
    3. ten dollars if the denomination is ten cents or greater but less than one dollar;
    4. five dollars if the denomination is five cents; and
    5. twenty-five cents if the denomination is one cent.

    -
    Rod (Canadian)

  31. The Math is just WRONG. Here's why by goombah99 · · Score: 3, Insightful

    The Deivation assumes two falacies
    first,
    that the price of goods is not partly determined by the demoninations of coins. for example, the reason why a candy bar is 50 cents or 65 cents and not say 48 cents is because we have nickels dimes and quarters. or that the reason a price is 5.95 cents and not 5.96 cents. etc..

    Second,
    this assumes your change purse is stocked with all denominations. that's true at the cash register but not in my pocket. When I reach in my pocket and I pull out some change there are a myraid of ways I can make 25 cents. 5 nickels, 2 dimes and a nickel, 5 pennies+ etc...,
    not so with his optimal set. if I'm nissing any of the denominations its hard to make it up with the others.

    third, entropy
    again reaching for change in my pocket the goal is not to find the minumum number of coins but rather to be able to pay the bill without thinking too much. that is the more ways I can add up to the same value the more likely I will on a random grab find the right coins to make it. I dont care how many coins.

    --
    Some drink at the fountain of knowledge. Others just gargle.
  32. Pirates by uberdave · · Score: 4, Interesting

    Back in the long ago, people used to do this. Spanish coins could be broken into eight pieces: "Pieces of Eight". The whole coin was the equivalent of a dollar, so a quarter would literally be a quarter of the coin, or two bits.

    1. Re:Pirates by Martin+Blank · · Score: 4, Informative

      Almost. The piece of eight (the Spanish Milled Dollar, worth eight reales) was one of the principal coins of the colonies, but the coin was not broken up. Instead, coins of values equivalent to one-half, one-quarter, and one-eighth of a dollar. One piece of eight was worth on real, eight reales to a dollar...

      And now you know.

      --
      You can never go home again... but I guess you can shop there.
    2. Re:Pirates by uberdave · · Score: 2, Informative
      This site, and Item 17 on this webpage would seem to cast some doubt on your objection.
      Due to a chronic shortage of "small change" throughout America's colonial period, the practice of cutting quarter, half and whole Spanish dollars into "bits" was commonplace.
      Once smaller silver coins became widely available during the 1800's, the crudely cut pieces of eight were melted down into silver bullion or exchanged for newly minted coins. Coin collectors of the period apparently showed little interest in collecting cut pieces of eight since the date and other identifying characteristics were often missing. Consequently, most surviving examples of this American tradition are generally found only at archeological sites.
  33. Two funny (sad) arithmetic stories by blahedo · · Score: 4, Funny

    A few years back, my dad was paying for something, and paid an uneven amount in order to get even change. The clerk looked at the money, sort of shrugged, and punched it in and started counting out the change. The catch is---my dad misheard the amount. So when the clerk started counting out a bunch of pennies and nickels, my dad was like, "wait, what?" Had the clerk had *any idea* why my dad had given an uneven amount, she would have realised that he'd misheard the price. But she just punched it in and started counting it out....

    A few years after that, my sister (in 5th grade at the time) had a test with a miscalculated grade, and when my mom went in for a parent-teacher conference, she brought it up. In particular, she said she'd added up the number correct and divided by the total number of questions, and got a different percentage... the teacher looked down her nose at my mom and said, "that's *not* how it's calculated." How was it calculated? Well, you have these cardboard discs that you turn according to the total number of questions, and then you read the grade out of the little window corresponding to the number right.... This woman had only the vaguest notion that this grade was a percentage correct, and *no idea at all* that---as a percentage---it could also be calculated by dividing the numbers out. None.

    --
    ``This, too, shall pass.'' ---Eastern proverb
    1. Re:Two funny (sad) arithmetic stories by SEWilco · · Score: 2, Funny
      Well, you have these cardboard discs that you turn...

      Yes, I know that some teachers just spin the wheel for grades.

      (+1.2, Funny)

  34. 5?! -Interesting +Utter Crap by Anonymous Coward · · Score: 5, Informative

    Cecil has the right answer instead of this complete conjecture.

    1. Re:5?! -Interesting +Utter Crap by cpeikert · · Score: 2, Insightful

      Hmm, is this more support for the argument that people are getting dumber?

      It says that the practice didn't start catching on until the 1920s, when merchants would under-price things at .95 and .99 to convince gullible people that they were getting "a bargain."

      So there must be a *lot* of suckers out there today...

  35. It's one better... by Graff · · Score: 4, Funny

    Hey, I can beat this guy at this math thing. According to my calculations there are much more efficient combinations. For example, if you use the coins 1, 2, 4, 8, 16, 32, 64 it will take approximately 3.19 coins per transaction (this is simple binary arithmetic). That's way better than his system which takes 3.89 coins per transaction. The only problem is that the geeks will do just fine with these denominations but just try and ask the average waitress to make change using those coins. Go ahead and ask, I'm sure it will work out just fine! :)

    You know, if we mint 1 coin for every amount of change (like a 57 cent coin, a 58 cent one, etc.) then it will only take 1 coin per transaction. Of course then we have to worry about having 99 different coins, making them distinguishable from each other, etc.

    The current United States system of currency works just fine. Denominations of 1, 5, 10, 25 are easy enough to calculate and efficient enough for all intensive purposes. Sure this proposed new system may be 17% "more efficient" for a computer but real people need to use the system also.

    Some things are best off just left alone...

  36. optimization is no non-trivial by pioneer · · Score: 2, Informative

    with denominations that do not divide evenly into each other it is non-trivial to find the optimal change for a given transaction.

    whereas with the US denomination (and most denominations are designed for this reason) you can use a greedy algorithm to give back change (always choose the largest coin possible, repeat) and you are guaranteed to be giving back the fewest coins.

    you can prove that a greedy algorithm provides an optimal solution if the problem has optimal substructure and the greedy choice property.

    To prove optimal substructure consider a collection of coins for an optimal solution, $c_1, ..., c_k$, such that $\Sigma_{i=0}^k = n$ where $n$ is the amount of money in cents to change. Assume that we remove the coin with the largest value. The remaining coins, $c_2, ..., c_k$, represent the solution to the sub problem of changing $(n - c_1)$. If $c_2, ..., c_k$ is not optimal there exists another set of coins for this subproblem, $x_2, ..., x_k$, such that this solution has fewer coins. However this is a contradiction because we can now form a solution for the original problem, $n$, by combining $c_1$ with $x_2, ..., x_k$ that has a smaller size than the original optimal problem. This is a contradiction and hence $c_2, ..., c_k$ is an optimal answer to the subproblem and therefore the coin changing problem exhibits optimal substructure.

    To prove the greedy choice property we must show that a globally optimal solution can be arrived at by making a locally optimal, this is, greedy, choice.

    For this particular set of American denominations we can prove the greedy property with a proof by contradiction. If the greedy choice were not optimal there would be an optimal collection such that:

    1. some set of dimes, nickels, pennies added to more than 25 cents or

    2. some set of nickels, pennies added to more than 10 cents or

    3. some set of pennies added to more than 5 cents

    However, all of these situations are impossible. If some set of pennies add to more than 5 cents, simply replace 5 pennies with a nickel (the greedy algorithm is better). If some set of nickel and pennies add to more than 10 cents and if there are two nickels, replace them with a dime; If there are a nickel and the rest pennies,
    replace a nickel and 5 pennies with a dime. The same holds for a quarter. If three dimes, replace it with a quarter and a nickel. If it's two dimes and nickel/pennies, replace it with a quarter. And so on... The property of the coins that results in the greedy property is that each coin denomination divides evenly into the next larger coin denomination. Therefore each larger coin denomination that is removed must be replaced by at least two additional coins.

    With non-even denominations you are required to actually search an n^2 space for the correct set of denominations. in fact, the algorithm is:

    $C(n) = 1 + min \{C(n-d_1), C(n-d_2), ..., C(n-d_k)\}$.

    Additionally, $C(n) = 0$ for $n = 0$. We can ignore $n 0$ are we just define $C(n 0) = \infty$. By building the array in time/size $\Theta(nk)$, and keeping track at each step which value of was chosen for the minimum, then we can list the coins by tracing backwards through these recorded values. This augmentation takes no additional time since it can be done during building the array in time $\Theta(1)$.

    So, basically you've changed the problem from a linear time algorithm in the amount of change to a quadratic time algorithm in the amount of change...

    GOOD LUCK WALMART EMPLOYEES!

  37. What about a 2 cents coin ? by rklrkl · · Score: 2, Insightful

    An 18 cent coin just seems silly to me, because the calculations required to use it would be difficult to easily optimise in your head. In the UK, we have a 2p coin [ironically, one of the largest-diametered in circulation] and wouldn't this cut down the number of coins needed in an easily calculable way ? It seems to me, that ease of change calculation is as equally important as the average number of coins used for said change, but this is almost glossed over in the article by one sentence.

  38. Actually, ... by Psychic+Burrito · · Score: 2, Insightful

    The computer tells the cashier to give back 98 cents, not "6 times the coin 18, ..." etc.

    So your argument is moot: The cashier does actually have to use math to give you back your change.

  39. OT: was- Re:I hate math... by bryan1945 · · Score: 3, Funny

    Pennies are worthless?!?!?

    Meet my penny-filled sock, my friend! And the sock is stinky, too!

    (Gimme a break, it's noon on Friday and I'm bored outta my mind...)-

    --
    Vote monkeys into Congress. They are cheaper and more trustworthy.
  40. Count by 18. Ready? Go! by jjohn · · Score: 2, Funny

    <voice style="school house rock">

    18...36...54...72...90....108

    STOP

    Multiply by 18 is like multiplying by 20 but subtracting multiples of 2. So 18*3 is really like 20*3 - 2*3. That's just 60 - 6, or 54! Let's do it again!

    18...36...54...72...90...108...126...144...162.. .180!

    Ready or not, here I come!

    </voice>

    no, I didn't use a calculator. I sure hope the math is right.

  41. Re:What we need is widespread acceptance of $1 coi by anderm7 · · Score: 2, Funny

    Forget $1 coins, I want a $1.0753875 coin so I can buy things that cost 99 cents.

  42. Once Again... by Hank+Reardon · · Score: 2, Interesting
    Once again, we have a novel solution to a problem that doesn't exist. Isn't life fun?

    I believe that what the researcher failed to take into account is the way that the human mind works. Adding 1's, 5's, 10's and 25's is definately easier than adding 1.37's or 83's for us.

    Sure, it may make the handing out of change more efficient by lowering the average amount of change given from 4.x to 3.x coins, but that efficiency will be more than lost when the clerks at the local mini-mart -- who already have problems giving out the correct change -- have to figure out that my $0.72 in change will be two 29-cent coins, two 5-cent coins and four 1-cent coins.

    Not to mention the increasing size of cash drawer shortages caused by less-than-mathematically-inclined clerks.

    Is it just me, or does it seem that the less "rounded" education becomes, the more one-dimensional "solutions" appear? Guess it is more true than ever: when all you have is a hammer, everything looks like a nail.

    /hr

    --
    There's so little difference between politics and jihad lately...
  43. A "Scientist" wrote this!?!?!?!? by radulovich · · Score: 5, Insightful

    This article is a complete waste of time. This might be a fun paper for a discussion about coinage, but it fails horribly when taken as practical advice.

    The US does not need another coin. Indeed, the *opposite* is true. If you get rid of the penny, you can increase efficiency tremendously, to only 2.75 coins per transaction, and a whopping 45% of transactions would require 2 or fewer coins!

    Many people oppose the elimination of the penny, but bear with me for a moment. Consider the following issues:

    - Pennies cannot be used in vending machines, and therefore are not as "spendable" as all the other coins.

    - Prices will not rise as people think they will; they will fall instead! Everything that is priced at $n.99 will now be $n.95 instead (marketers HATE to price in round dollars because it makes their prices look higher). All other numbers will be rounded to the nearest $n.n5.

    - The US government makes 12 billion pennies at a cost of $100 million each year (http://www.retirethepenny.org/), which could be put to better use than filling up my coin jar.

    - Half of these pennies will disappear from circulation within a year! (http://www.shepherd-express.com/shepherd/19/41/ne ws_and_views/straight_dope.html)

    - Counting out pennies costs the economy an estimated $20 billion in productivity annually (http://www.retirethepenny.org/)

    - The U.S. Mint loses $8 million a year manufacturing pennies. (http://www.shepherd-express.com/shepherd/19/41/ne ws_and_views/straight_dope.html)

    Think about it - do you *really* want another coin in your pocket? Thank God that politicians don't listen to us all the time!

    -Mark

    1. Re:A "Scientist" wrote this!?!?!?!? by prgrmr · · Score: 2, Interesting

      There is currently a bill in Congress, in committee, that proposes chaning the reverse design for three years (2007 - 2009) to commemorate the 200th anniversary of Lincoln's birthday, and then would discontinue the penny. It specifically spells out how rounding would be done for cash transaction (down in amounts ending in 1, 2, 6, & 7 and up in amounts ending in 3, 4, 8, & 9). Check and electronic transactions would continue to be for exact amounts of the total purchase. Rounding would be done only on the total amount, and after state sales tax is applied.

  44. Re:No, you're not retarded by mdielmann · · Score: 2, Funny

    It's just sometimes people like to do this to be helpful or just to be annoying/arrogant (really anticipating the look of panic in the cashiers eyes).

    I don't do it for any of those reasons. I mostly do it because I'm lazy and don't want to carry around 5 pounds worth of pennies. Oh, yeah, I also want the only jangling sound when I walk to be from my big brass ones. ;)

    --
    Sure I'm paranoid, but am I paranoid enough?
  45. Simpler Solution: Get Rid of the Penny by Enonu · · Score: 2, Interesting

    * 2.79 coins average per transaction given that getting 5 cents is just as probable as getting 95 cents, and that no 50-cent pieces are used.

    * Counting in 5's, 10s, and 25's is a lot easier.

    * Saving pennies, rolling them up, going to the bank, and then driving home is a pain-in-the-ass, and honestly isn't worth my time, e.g. 2 hours of work to get $10 of pennies?!?!?. It's more economical to throw the friggen ugly coins in the trash, but I can't do that out of principle.

    GET RID OF THE PENNY!

  46. Modest proposal by justfred · · Score: 2, Funny

    I prefer the following : make pennies worth $1.

    This would:

    -eliminate the penny,

    -give us a distinguishable dollar coin,

    -and stimulate the economy

    Pennies are visibly and tactilly different from our other coins; can be used in vending machines; are easy to carry around. Plus, Lincoln was a great guy, what with freeing the slaves and all (better than that indian-killer Jackson that's on the $20, at least) and this lets us honor him once again.

    Income would be redistributed somewhat randomly to people with big jars of pennies. The ultra-rich (you know, the ones getting the big tax cuts) probably have no more than a handfull of pennies. Some people would chose to hoard the new dollars; while others would spend them with abandon. And wouldn't you like to pay your taxes by sending in several rolls of pennies?

    Just for laughs, I'd make "wheat cents" worth $100.

  47. Pennies by notwhole · · Score: 2, Funny

    I just failed to find any of my one sided pennies....Curse you third dimension!

  48. Non-decimal systems have advantages by misterpies · · Score: 4, Interesting

    First, can't you tell a joke when you see one? (By joke I don't mean the maths is wrong, just that obviously the writer wasn't intending that we move to 18c coins).

    Second, what is easy is what comes with practice. Currencies, like most other measurement systems, were not originally decimal, but duodecimal (i.e. using base 12) and various multiples thereof. Right up to the 1970s, the UK used a currency system which had 12 pennies to a shilling and 20 shillings to a pound. The US and UK still use duodecimal for weights and measures (think pounds and feet) and the whole world uses it for time (12/24 hour systems) and angles (360 degrees is 30 times 12).

    Why were systems based on numbers like 6, 12, 24, 360 etc. so common, given that we tend to count in decimal? Well, they have large numbers of factors. In other words, while they might be harder to add and subtract in your head than decimal systems, they're much easier to do division with. And since division is much harder to do in mental arithmetic than addition, that's a big advantage.

    For example, with 12 ounces in a pound, I can take a half, a third, a quarter, a sixth or a twelth of a pound and still be dealing in whole ounces. With a decimal system, 10 has only 2 factors: 2 and 5. So to buy a quarter of something devised in a decimal system you end up with 2.5.

    Now that also has a knock-on effect when making change. Because of the limited factorisation of 10, most decimal systems divide things into 100s or 1000s.

    Result: in a decimal currency, you end up not with 10 cents per dollar, but with 100 cents. And that's the real reason you have so much change in your pocket. If we had 12 cents to the dollar (or euro), then by copying the old british system -- with a 1c, 2c, 3c and 6c coin -- you'd never need more than 4 coins to make change from a shilling.

    And would the cashier at WalMart be able to handle it? Well first off, maybe if as a result they had to think more as kids they'd be better off at maths to start with. And secondly, since they have to use a calculator now anyway, what would be the difference?

    --
    The author of this post asserts his moral rights.
  49. Don't get me started by Wansu · · Score: 4, Insightful



    It doesn't matter what the denomination is. As long as change has to be made, some patrons will receive the wrong change.

    Lots of cashiers don't know how to make change. Many have been trained to do it wrong. The most common error is the cashier puts the large bill the customer just handed them into the drawer before giving the customer change and watching them count it. There used to be a little slot between the plastic guard and the metal cash register enclosure that was perfect for temporarily storing that large bill in customer sight. When the customer looks at you after counting his money, pause to see whether he questions it, then put the large bill in the drawer and close it.

    Adding this momentary delay before putting the customer's large bill in the drawer and closing it, protects the cashier and the customer from being short changed.

    I've seen managers put large bills in the drawer before I counted my change. One gave me change for $10 instead of change for a $20. I'm a creature of habit. When I hand a cashier a large bill, I always say, "outta twenty" or whatever the bill is. I'm sure I did that with this one. But she'd already put the bill in the drawer and insisted upon a recount of the drawer and by the time she did, my food was cold. That is not the way to do things. When I pointed out her mistake, she lost her temper. Then I lost mine.

    I was trained on older cash registers to do things this way by a store manager who was very particular about this. He's been in business for more than 30 years and says he's never had a dispute with a customer over incorrect change. Way back then, you had to actually count the coin change. Many of the newer cash registers do this for you. I wonder how many of today's cashiers could make change in their heads.

    What's my point? Most point of sale problems concerning change making are due to lack of skill and/or poor training of the cashier. Using more efficient denominations or pricing items to the nearest buck won't fix this.

    --
    Wansu, th' chinese sailor
  50. Re:No, you're not retarded by medscaper · · Score: 2, Funny
    Oh, yeah, I also want the only jangling sound when I walk to be from my big brass ones.

    I don't think those Sacagaweas "ones" are really brass - they just look it.

    Sorry. Couldn't resist.

    --
    Any sufficiently well-organized Government is indistinguishable from bullshit.
  51. How does Walmart affect it? by KlomDark · · Score: 2, Interesting

    I'd be curious to see how the average distribution of change is affected by the dominance of Walmart and it's strange method of pricing where most things end up costing X dollars and 88 cents. With the significant percentage of money spent at Walmart, it seems that it would throw off his distribution method, so perhaps a different denomination coin would be more appropriate in dealing with the Walmartization of America.

  52. The writer TOTALLY doesn't get it. by Theovon · · Score: 2, Interesting

    The average cachier over the age of 18 barely managed to graduate highschool and is very unlikely to be able to do simple arithmetic. The average engineer I know making $80k+ also cannot do simple arithmetic.

    It's hard enough when you have to deal in 5's and 10's, but as soon as you start asking a cachier to add or subtract 18 from ANYTHING, you're going to have trouble.

    The whole problem here is that the author doesn't realize that humans are (a) not computers, and (b) don't care about handing out one less coin. The system we have, as imperfect as it is, evolved this way through error and natural selection. Sure, perhaps no one considered printing an 18 cent coin, but that's likely because they knew people would have trouble dealing with them. Humans inherently have trouble with simple arithmetic, so a system evolved that was less ERROR-PRONE, completely ignoring minor improvements in efficiency.

    So, of course, one has to ask the question: Could we make the system less error-prone? Probably. Maybe our esteemed computer scientist should develop a system to determine which coins we need to have in order to make it more likely for a cachier to give back correct change.

    What's better, taking 2 seconds longer to give you correct change or two seconds less to give you incorrect change? I'll wait the extra 2 seconds.

    Or maybe I'll just use my credit card.

  53. Re:*whap* by shreak · · Score: 2, Funny

    In Canada they have the Loony and Toony (denziens of the maple leaf state, please correct my spelling). These are $1.00CA and $2.00CA coins respectivly.

    A friend and I were in CA on business and were totally unable to figure out the stripper tipping protocol. We had a few USD which the ladies were happy to accept. But then we were down to "hard" CA currency.

    "Maybe you throw them?" I asked. Of course we didn't want to risk chipping a tooth.

    One of the ladies drifted over after a while and started talking. She was from the US and I asked her how it was done. She took a Loony from me and walked up to the stage, put it between her teeth and lay down on her back on stage. The performer at the time crawled up over her, mouth over mons, and crawled backwards and removed the coin with her breasts. Very Hot!

    She then gestured me over, obvously expecting me to do the same thing! Having spent some time in US strip clubs, this level of contact is strictly Verboten! Enough to get you ejected into the -30 CA winter air. My friend wasn't so shy and walked up and got the ride of his life!

    Canada may be cold in the winter but the ladies can be vary warm!

    =Shreak

  54. Re: Penny minting - Inflation? by js7a · · Score: 2, Informative

    Eliminating the penny just makes sense.

  55. Re:Instead...Japan, the land of confusion by hbackert · · Score: 3, Insightful

    Life gets more complicated when coming originally from Germany, where VAT is always included in the advertized price (for end-users, not for businesses) and going to Japan, where 5% tax is mostly added. About 90% of all times I need to add 5% at the cashier. In the other cases I don't need to. Now that makes calculation the price to pay complicated.