Cold Hard Cash

On Sunday H9 showed me something that I did not know. We were standing on the subway platform and he decided to perform one of his rituals, namely where he checks the returned money slot on a vending machine in the hopes of increasing his investments and helping to provide for me when the pension system collapses.

Anyway, he found a coin. And he asked me to feel the coin. It was warm, and coiny. Then he said “Watch!” and put the coin into the slot and pressed the return button.

The coin re-emerged at the bottom and he popped it into my hand. It was now very cold. Hmmm, I though, interesting. I started to check out the machine, wondering how it happened.

The coin slide must be close to the cooling system, I reasoned. Maybe too close. Maybe there was a leak. But it must have been a very efficient system to cool down a metal coin that quickly. Or a very big leak. Hmmm…

And then the kid stared at me funny and said,  “But it’s not the same coin, of course.”

“What?” I said.

“It’s not the same coin. They don’t return the same one that you put in.”

A light came on in my head, and so we performed a quick experiment. We marked the coin, popped it back in and pressed the return button. And out popped an entirely different coin, nice and cold, with no marks.

So the kid was correct, and taught his old man a lesson in the art of being skeptical, of not accepting things on face value, of questioning your long-held beliefs in the light of new evidence, and looking for the most obvious solution to a problem.

That’s my boy.

/ paddy

11 thoughts on “Cold Hard Cash

  1. Good on you kid! We all need new perspectives now and then… As someone once said: Keep it simple, stupid! or KISS! Or as Einstein put it: Keep it as simple as possible, but not simpler.

  2. Ah over-thinking, not good. You still have to much scientist in you. I had all that knocked out of me when I worked in The City. I saw “different coin” the moment you mentioned the problem. I assume the first coin was warmed up by your friend’s hand to prove a point.

    On my first day at university, an old long-haired Canadian professor introduced me to the KISS principle. I have stuck with it ever since. That and my grandfather’s “patience is a virtue”. Heard it afore but my grandfather (old soldier, anti-treaty IRA) gave it gravitas so that stuck too.

    My lived in an out house by the stables because the house fell down. A single room for 30 years. I just realised that I am the same. It was pointed out to me that no matter how large a house I live in, I gravitate to one room. Live, sleep and eat in it. Keeping it simple in all aspects of life.

    Back to eating my home grown tatties.

  3. ladyfi: Keep an open mind, but not so open that your brains fall out.

    James: Why should it be simpler to return a different coin than the same coin? I think it is simpler that the coins are kept in storage just before the coin box and are returned or allowed in depending on what happens with the transaction. Why is this more complicated than the other way?

    But yes, I should have seen the solution more quickly.

  4. Well done, Junior!

    But I wonder. The machine must have two different mechanisms to return coins. One for when the customer sticks a foreign or very old coin into the slot, which the machine returns. And one for refunds.

  5. I agree with Stuart. That autistic kid made a giant ass out of you and then caused you to blog about it online, making an even bigger ass out of you. I’d find out where that wise-ass kid lives and beat the f^%@ out of him. (Steal his tasty Halloween candy whlie you’re at it.) That’ll teach him, and good. Hehehe.

  6. > Why should it be simpler to return a different coin
    > than the same coin?

    It’s a programmer’s solution. You have a stack of coins. Is it easier to push a new coin on to the top of the stack, or in under the bottom of it?
    Is it easier to pop a coin from the top of the stack or from the bottom of it?

    I’d say it’s easier to pop the coin from the bottom of the stack. If you used the same chute as for the refused coins you would need an extra lead back to the refused chute. Probably more complicated. What guarantee do you have that the stack of coins will always be high enough to have a coin to fall down the refused chute? Popping from the bottom means you never need to lift the coin, you only need to use simple gravity.

    Then again, I don’t exactly *know* how that machine is constructed. They might have solved it in another way entirely. Somebody interested enough to contact the company and find out how it really works?



  7. Martin, the machine also has to make arbitrary amounts of change – ie it has to be able to pay out whatever credit balance it contains after you make your purchases. So I assume that when you press for a refund what the machine actually does is a “pay the credit balance” action rather than a “return the coin” action.

    The mechanism for rejecting foreign coins is probably completely separate since these are never credited.

  8. Everybody: You are all very smart people, with very interesting comments. And I am a lazy git so I won’t reply to each one. But I agree – the mechanism seems to be run as a stack. Possibly to prevent 50s children from putting in coins with strings on.

  9. Oh, I learnt that a few days ago. A friend of mine threw in two 50örecoins and pressed the “change”-button, and got two 1kronor back. Also, they showed how to haxx a Cola-machine, pay for one, get two!

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