How do you determine which stack is counterfeit with only one weighing?

3 Responses to “How do you determine which stack is counterfeit with only one weighing?”

1. bob h says:

   October 26, 2009 at 5:51 pm

   take 1 coin from stack 1
   2 coins from stack 2
   3 coins from stack 3
   etc.

   weigh the coins.

   they will weigh a little less than 110 ounces
   the number of ounces less than 110 ounces
   is the counterfeit stack
2. rfamilymember says:

   October 26, 2009 at 5:51 pm

   take 1 coin from the first stack,2 from the second,3 from the third and so on and thus in one weighing you will know which stack is counterfeit
3. benoit3535 says:

   October 26, 2009 at 5:51 pm

   Put 1 coin from the first stack on the scale, 2 from the second stack, 3 from the third stack, etc… That’s a total of 55 coins on the scale. If they were all good the weight would be 110 ounces.

   If there’s 1 ounce missing (109) then there’s one bad coin so it comes from the first stack.

   108 would mean 2 bad coins, so 2nd stack. Etc.