Mental calculations

problem

Prime Magic

Age

7 to 16

Challenge level

2 out of 3

Place the numbers 1, 2, 3,..., 9 one on each square of a 3 by 3 grid so that all the rows and columns add up to a prime number. How many different solutions can you find?
game

Domino Magic Rectangle

Age

7 to 16

Challenge level

3 out of 3

An ordinary set of dominoes can be laid out as a 7 by 4 magic rectangle in which all the spots in all the columns add to 24, while those in the rows add to 42. Try it! Now try the magic square...
problem

Street Lamps

Age

11 to 14

Challenge level

1 out of 3

Walking up a steep hill, I pass 10 equally spaced street lamps. How long do I take to walk from the first lamp to the last?
problem

Is It Magic or Is It Maths?

Age

11 to 14

Challenge level

2 out of 3

Here are three 'tricks' to amaze your friends. But the really clever trick is explaining to them why these 'tricks' are maths not magic. Like all good magicians, you should practice by trying them. Can you explain how they work?
article
Let's Get Flexible!

In this article for primary teachers, Ems outlines how we can encourage learners to be flexible in their approach to calculation, and why this is crucial.
article
Clever Carl

What would you do if your teacher asked you add all the numbers from 1 to 100? Find out how Carl Gauss responded when he was asked to do just that.