Puzzles index

Weighing balls puzzle

There are twelve balls. You know that eleven of them are the same weight, and one is different. You do not know whether the different ball is lighter or heavier. You have a balance set of scales, so you can weigh one set of balls against another set. You are only allowed three weighings in all. Can you work out which ball is a different weight from the others? Can you work out whether it is heavier or lighter? How should you weigh the balls?

This puzzle involves quite a lot of work as you have to work out the result of all possible results from the weighings that you have chosen. But write them down and think about them, and see how far you can get.

Click here to see the solution but think about it yourself first! The explanation is more fun, and makes more sense, after your own attempts. There is a further discussion here.