During the Numeracy Hour (for UK schools), there is a big emphasis on getting children to have lots of mental practice. I have devised a good game which the children enjoy playing.

Write the numbers from 1 to 20 up on the board and think of a number.  The children have to guess what your number is by adding two numbers together or taking two numbers away.  The children love it and the the numbers also act as a number line.

Differentiation:

- Children who operate at an lower level can contribute through asking other relevant questions, e.g. is it less than / more than etc.

- For older / more able children, you can make the number line bigger (up to 30, 40 etc.)

This activity is a brillant time filler as well.