
How much change is in a vending machine?  - wglb
http://www.pagetable.com/?p=353
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donw
I'm a big fan of estimation:

If you've ever seen the guys refilling the machine, you know it's got a slot
for every drink button. There are about eight buttons on the average machine,
and I'm guessing that each row holds about a case of soda -- 24 units (cans or
bottles).

So, that's 192 refreshing beverages per machine.

Now, they don't just wait until everything is empty to refill, and not every
customer is going to pay with two $1 bills. So, let's make a couple of
assumptions:

1\. They refill the machine when it's about half-empty, so you only need
change for about half of what the machine holds.

2\. If you put in $2, you get back $0.75 in change (if the soda is $1.25), but
we don't need to do that every time.

3\. Given the usage patterns that I've observed, I'm figuring that we only
need to provide change for about every third bottle, so we need about a
quarter for every drink unit that we sell.

Put those together, and you get $24 in change.

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pmccool
This assumes that the change dispenser is emptied at the same time that the
machine is refilled. This is a reasonable assumption, but not a self-evidently
correct one.

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VengefulCynic
I know in the grocery store (in the US) where I worked in high school, this
was incorrect. The store was responsible for sticking the change, the armored
truck was responsible for collecting the receipts, and the vendor was
responsible for stocking the product. Granted, this is the most complex case
and relies on the abnormal relationship that vendors have with supermarkets,
but I would suspect that it represents a nontrivial percentage of machines.

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michaelfairley
In most vending machines, inserting a coin and then hitting the change return
button will return a different coin than the one that was inserted. Do this a
large number of times and you will likely see all the coins. (Also useful for
collecting the state quarters.)

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benbeltran
When I was a high school student, a friend found a brute force attack that
worked on the machine in our campus (ie. kicking it right below where the
coins go).

I can say he reached a similar result.

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Mankhool
I'm not interested in this question per se, however I am interested in vending
machine design. It is only recently that some vending machines are able to
take my money AND dispense my purchase (soda pop) fairly near waist level
(3-4ft from the ground). However, the change dispenser of this machine is
still less that 12" from the ground meaning serious bending over or kneeling
to obtain the change. Why cannot change be dispensed at the same height as
money in and product out - especially if there is a separate dispenser for it?

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VengefulCynic
The design for the change dispenser is predicated on the same design principle
as the soda dispenser: maximize the storage for items to be dispensed and
utilize gravity to do the dispensing. If you move the slot up, you either
change the dispensing mechanism or you reduce the quantity stored.

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dublinclontarf
Vending machines in Ireland(my home country) don't have a change button, they
have a return coin button(no notes usually). And once you have bought
something, if there is no change in the machine it won't give you any back.

Some vending machines have small lcd's that say no change when out, most
don't. And a can that should have cost Euro0.80 has now cost Euro1 or if your
unlucky then Euro2(if you used the two Euro coin).

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stretchwithme
Lets find out by tipping it over!

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philwelch
I don't know why this was modded down--it's a valid solution in the finest
tradition of the Gordian Knot: <http://en.wikipedia.org/wiki/Gordian_Knot>

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stretchwithme
Sorry, I don't know what you mean. I just left my comment, which was just a
joke about tipping over the vending machine, a common practice when you want
to find out whats in it. Sorry for any confusion.

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philwelch
Wikipedia is down, so I'll tell the story as far as I remember it:

There was an infamous knot called the Gordian Knot. It was an actual knot,
very difficult to untie. There was some prophecy or other that the person who
was able to solve the Gordian Knot (by presenting the two separated ends of
the knot) would rule all of Asia or something. Anyway, Alexander the Great
faced the knot, carefully considered the problem for a minute or two, drew his
sword, and cut it in half.

So a Gordian Knot is something that seems to be a complex intellectual puzzle
you can spend a lot of time and effort meticulously working at, or you can
just "cheat" and get the same result out of it, and it doesn't really matter
in the end. There's a similar joke about a mathematician, a physicist, and an
engineer finding the height of a building--the mathematician measures the
building's shadow and the angle of the sun and derives the answer with
trigonometry, the physicist drops a stopwatch off the roof and derives the
height from the time on the stopwatch when it hits the ground and breaks, and
the engineer steps inside and asks the superintendent how tall the building
is.

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tobych
"Wikipedia is down, so I'll tell the story as far as I remember it..."

Your introduction warmed my heart. An air-conditioning plant fails in Florida
and the art of storytelling from memory is rekindled.

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rokhayakebe
Why not just wait until the guy who changes the food comes in and ask him?

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jws
You could offer a barometer in exchange.

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GFischer
this references the "barometer problem" legend:

<http://www.snopes.com/college/exam/barometer.asp>

