Write a list of four or five numbers in a line. They should all be answers in a certain times table except one number which should be the `odd one out`.

The children need to find the odd number and be able to say why.

For example:
16, 64, 27, 8, 32
The odd one is 27 as the others are in the 8x table.

This can be as easy or hard as you like according to the age and ability of the children. You could also change the list so that it includes concepts from other subjects (e.g. find the odd one out in a list of countries).