Copyright © University of Cambridge. All rights reserved.

## 'Money Measure' printed from http://nrich.maths.org/

You have ten identical open-topped boxes with 10 visually identical coins
in each.

In nine of the boxes each of the 10 coins has a mass
of 10g.

In one box the 10 coins have masses of only 9g each.

How can you find which box is the odd one out?

You have a normal mass measurer with a single pan and a scale. With just
one weighing you can identify the box with the lighter coins.

What will you weigh?