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Polydron

This activity investigates how you might make squares and pentominoes from Polydron.

Construct-o-straws

Make a cube out of straws and have a go at this practical challenge.

Cereal Packets

How can you put five cereal packets together to make different shapes if you must put them face-to-face?

Cuisenaire Squares

Age 7 to 11 Challenge Level:
You could use some Cuisenaire rods to have a go at this problem or you could use this interactivity.
Alternatively, drawing rods on squared paper might help.