Thirty €1 coins are arranged in a circle on a table. Ten of these coins are fake and a little lighter than the 20 real coins. You don’t know where in the circle the fake coins are, but you have been ...

In recent years a number of clever coin-weighing or ball-weighing problems have aroused widespread interest. Here is a new and charmingly simple variation. You have 10 stacks of coins, each consisting ...

Rumors often circulate about the 50-rupee coin. This has led many shopkeepers to shy away from accepting 10-rupee coins. However, you might be surprised to learn that a total of 14 different designs ...