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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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Diagonal Trace

You can trace over all of the diagonals of a pentagon without lifting your pencil and without going over any more than once. Can the same thing be done with a hexagon or with a heptagon?

Number Differences

Stage: 2 Challenge Level: Challenge Level:1

Try putting any number in one square to start with.
What numbers could go in the squares which join this first square? What do all these options have in common? Can this help you find other arrangements of the numbers?
You might like to print out this sheet of blank grids if you are not using the interactivity.