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

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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!

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Is it possible to rearrange the numbers 1,2......12 around a clock face in such a way that every two numbers in adjacent positions differ by any of 3, 4 or 5 hours?


Age 11 to 14 Challenge Level:

Six points are arranged in space so that no three are collinear.

How many line segments can be formed by joining the points in pairs?

If all the line segments are coloured either red or green prove that there is a triangle all of whose sides are of the same colour.