# Coin Balance

### From Mycoted

There are 12 boxes each containing a coin. There are a total of 11 pennies and 1 other coin in the boxes. You have a balance scale for comparing the weight of the boxes in which you can put any number of boxes on each side. You have at most, three weighings. In these three weighings you must find out which of the 12 boxes has the coin that is not a penny.

Answer | |
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Balance any 4 coins (and call them A) with any other 4 coins (and call them B).
As case 2, but swap all heaver / lighter.
1. Divide the coins into two groups, each containing six coins. Weigh the two groups and set aside the lighter group. 2. Divide the heavier group into two stocks, each containing three coins. Weigh these two stocks, setting aside the lighter stock. 3. Weigh two coins from the heavier stock against each other. If either coin is heavier, then the heavier coin is not a penny. If the coins weigh the same amount, then the third coin in that stock is not a penny. | |