The Twelve Coin Balance Problem

This is a classic old puzzle which requires logic, lateral thinking and a lot of patience! (Sometimes the puzzle features billiard balls instead of coins, but the problem is the same.)

The Problem:

• You are given twelve identical coins.
• You are told eleven of them weigh exactly the same but one is a fake which is either heavier or lighter than the others.
• You have set of balance scales, and you have to find which is the fake, and whether it is too heavy or too light.
• The tricky bit is that you are only allowed to use the balance scales a maximum of THREE times!

Would you like to know the full solution? If you can't do the normal puzzle, then look at these 12 old coins. The fronts and backs of all the coins are shown, can you spot the FAKE? Click on it for the answer.

Here's what posh scales look like.

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This solution to the Twelve Coin Balance Problem is copyright © Kjartan Poskitt 2004 and may not be reproduced in any form for commercial gain without permission. Thank you.