PROBLEM. Among three coins of identical appearance one could be false and of different weight from the other two. Using a twin-pan balance to compare the coins’ weights, find the false coin if there is one, and in this case determine whether it weighs more or less than the other two with no more than two weighings.
The solution is very simple. We invite you to find it on your own before going on in our discussion, which will become progressively more complicated and, we hope, more interesting.
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