Choose a couple of the sequences. Try to picture how to make the next, and the next, and the next... Can you describe your reasoning?
The triangle ABC is equilateral. The arc AB has centre C, the arc BC has centre A and the arc CA has centre B. Explain how and why this shape can roll along between two parallel tracks.
A triangle ABC resting on a horizontal line is "rolled" along the line. Describe the paths of each of the vertices and the relationships between them and the original triangle.
An animation that helps you understand the game of Nim.
Can you describe what happens in this film?