This challenge is accessible to all pupils - everyone can have a go - but explaining why it is impossible with certain shapes is more difficult. It is a good context in which to encourage pupils to make conjectures and to verify them.

Do you have a system fortrying to trace over the diagonals?

What do the shapes that work have in common?

Which other shapes do you think it will work for?

The problem Networks and Nodes would be a good follow-up challenge to this one.

This sheet , with six of each shape and their diagonals drawn, will be useful to print off for some pupils.