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List any 3 numbers. It is always possible to find a subset of adjacent numbers that add up to a multiple of 3. Can you explain why and prove it?

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Magic Sums and Products

How to build your own magic squares.

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Nine, Ten and One

Weekly Problem 3 - 2013
Can you find the value of t in these equations?

No Matter

Age 11 to 14 Short Challenge Level:

Think of a whole number, double it, then add 3. Multiply your answer by 4 and from this take away 5. Now also take away the number you first thought of.

No matter what your first number was, your answer will be a multiple of which number?

This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.