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Calendar Capers

Choose any three by three square of dates on a calendar page...

Adding All Nine

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!


Draw a 'doodle' - a closed intersecting curve drawn without taking pencil from paper. What can you prove about the intersections?

Take Three from Five

Age 11 to 16
Challenge Level

Start with the problem What Numbers Can We Make?

Think of a simpler problem:

If you choose two integers from a set of three integers, you can always select two integers that add up to an even number. Can you explain why?