problem Isosceles Seven Age 14 to 16 Challenge level Is it possible to find the angles in this rather special isosceles triangle?
problem Triangle in a Square Age 7 to 11 Challenge level Do you agree with Badger's statements? Is Badger's reasoning watertight? Why or why not?
problem Possible Pairs Age 7 to 11 Challenge level In this game, you turn over two cards and try to draw a triangle which has both properties.
problem Triangle or No Triangle? Age 5 to 7 Challenge level Here is a selection of different shapes. Can you work out which ones are triangles, and why?
problem Name That Triangle! Age 7 to 11 Challenge level Can you sketch triangles that fit in the cells in this grid? Which ones are impossible? How do you know?
problem Triangle transformation Age 7 to 14 Challenge level Start with a triangle. Can you cut it up to make a rectangle?
article Peg and Pin Boards This article for teachers suggests activities based on pegboards, from pattern generation to finding all possible triangles, for example.
problem Three Triangles Age 7 to 11 Challenge level What do you notice when you put three triangles together?
problem Constructing Triangles Age 11 to 14 Challenge level Generate three random numbers to determine the side lengths of a triangle. What triangles can you draw?
problem Walking round a triangle Age 5 to 7 Challenge level This ladybird is taking a walk round a triangle. Can you see how much he has turned when he gets back to where he started?