Show that is it impossible to have a tetrahedron whose six edges have lengths 10, 20, 30, 40, 50 and 60 units...

Can you use small coloured cubes to make a 3 by 3 by 3 cube so that each face of the bigger cube contains one of each colour?

How many winning lines can you make in a three-dimensional version of noughts and crosses?

Imagine you have an unlimited number of four types of triangle. How many different tetrahedra can you make?

The edges of a cube are stretched, can you find the new surface area?

Which faces are opposite each other when this net is folded into a cube?