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A game for two people, or play online. Given a target number, say 23, and a range of numbers to choose from, say 1-4, players take it in turns to add to the running total to hit their target.

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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?

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What is the smallest number of answers you need to reveal in order to work out the missing headers?

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A game in which players take it in turns to choose a number. Can you block your opponent?

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The clues for this Sudoku are the product of the numbers in adjacent squares.

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Play the divisibility game to create numbers in which the first two digits make a number divisible by 2, the first three digits make a number divisible by 3...

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Sets of integers like 3, 4, 5 are called Pythagorean Triples, because they could be the lengths of the sides of a right-angled triangle. Can you find any more?

This article explains various divisibility rules and why they work. An article to read with pencil and paper handy.