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Two of the numbers in a 4x4 magic square have been swapped. Can you work out the sum of these numbers?

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Can you work out the sum of the missing digits in this subtraction?

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The sum of each column and row in this grid give the totals as shown. What number goes in the starred square?

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Weekly Problem 21 - 2010

How many diagonals can you draw on this square...

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In the multiplication table on the right, only some of the numbers have been given. What is the value of A+B+C+D+E?

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Four cards have a number on one side and a phrase on the back. On each card, the number does not have the property described on the back. What do the four cards have on them?

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What is the smallest number of jelly babies Tom must take, to be certain that he gets at least one of each flavour?

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Each interior angle of a particular polygon is an obtuse angle which is a whole number of degrees. What is the greatest number of sides the polygon could have?

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What is the largest number Sophie can use to have seven positive integers with a mean of 7?

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Can you place the nine cards onto a 3x3 grid such that every row, column and diagonal has a product of 1?

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In a 7-digit numerical code, each group of four consecutive digits adds to 16, and each group of five consecutive digits adds to 19. What is the sum of all 7 digits?

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Can you make the numbers around each face of this solid add up to the same total?