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Number Detective

Follow the clues to find the mystery number.

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Red Even

You have 4 red and 5 blue counters. How many ways can they be placed on a 3 by 3 grid so that all the rows columns and diagonals have an even number of red counters?

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Prime Magic

Place the numbers 1, 2, 3,..., 9 one on each square of a 3 by 3 grid so that all the rows and columns add up to a prime number. How many different solutions can you find?

Various Venns

Age 7 to 11 Challenge Level:

Where would you put a number which is square but not odd?
Where would a square odd number go?
Where would a number which is odd but not square go?
Where would you put a number which is not square and not odd?
You could try placing each number in turn. For example, is $0$ a square number? Is it an odd number?