Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!

Is there an efficient way to work out how many factors a large number has?

15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?

Work backwards.

Simplify the game by choosing a smaller target and working out a winning strategy.

Play the game against the computer and think about the computer's strategy.