I have a problem with some counterfeit coins...

DRZ

DRZ

DRZ

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In front of me I have ten bags containing several coins and I don't know how many coins are in each bag. I do know that ONE of the bags of coins contains counterfeit coins and that each counterfeit coin ways one gram less than a real coin.

I have the ability to weigh the coins but I can only use the scales once - how can I find out which bag contains the counterfeit coins?

Note:

You don't know how many coins are in each bag so you cannot assume they are all the same.

Using the scales once means a single use - ie you cant go putting things in, getting a reading and then taking things out to get another reading.

Good luck!
 
Or juggle the bags, the one which follows a different arc obviously has a differnet weight.
 
SB118 said:
Or juggle the bags, the one which follows a different arc obviously has a differnet weight.
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But they don't all have the same amount of content (no# of coins).

basmic said:
Slowly add each bag of coins to scales, noting the weight after adding each bag.
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But they don't all have the same amount of content (no# of coins). And he can only take ONE reading from the scales.
 
paradigm said:
But they don't all have the same amount of content (no# of coins). And he can only take ONE reading from the scales.
Click to expand...
DRZ said:
Using the scales once means a single use - ie you cant go putting things in, getting a reading and then taking things out to get another reading.
Click to expand...
So the way I see it, he can take as many readings as he wants, before 'taking things out'. ;)
 
This one is easy (Once you've done it before ;) )

Take 10 coins from the first bag, 9 from the second bag, 8 from the third bag and so on and place them all on the scales. The number of grams the actual weight is under what the weight should be if all the coins were real (I'm assuming you do know the weight of real coins, but if you don't you can't solve it) is the bag number with the fake coins in it.
 
Spuds said:
This one is easy (Once you've done it before ;) )

Take 10 coins from the first bag, 9 from the second bag, 8 from the third bag and so on and place them all on the scales. The number of grams the actual weight is under what the weight should be if all the coins were real (I'm assuming you do know the weight of real coins, but if you don't you can't solve it) is the bag number with the fake coins in it.
Click to expand...
I was thinking along these lines but we have nothing to compare the weight too.
 
or take em to your nearest back street shop and buy something or change yar money up much easiesr than all this messing around ;)
 
Add bags 1 by 1 and divide by the number of coins in each bag.

e.g. 1st has 6 coins in and weighs 60 grams, each coin is 10 grams, 2nd has 5 coins in and weighs 50 grams, 110 grams on the scale, each coin is 10 grams as well, 3rd has 6 coins in but weighs 54 grams, now 164 grams on the scale, each weighs 9 grams
 
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Take 1 coin from each bag...

Add coin 1 to the scales...

Weight = 5grams

Add coin 2 to the scales...

Weight = 5grams

5 + 5 = 10

Add coin 3 to the scales...

Weight = 4grams

10 + 4 = 14

Coins 3 is the fake?
 
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