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Rolling Triangle

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.

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Turning Triangles

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.

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Notes on a Triangle

Can you describe what happens in this film?


Stage: 2 and 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Understanding Nim

There are many internet resources that will tell you how to win at Nim, but at NRICH we found them all to be rather unsatifactory. Sometimes it's not enough to know the secret of winning - and the curious amongst us want to know why it works and how it was discovered. With those thoughts in mind, we've developed an animation called 'Drips' that we hope will allow you to discover the secret for yourself. It's still not totally straightforward so be prepared to dwell on the problem for some time. You will find the animation at It's tablet and phone friendly.

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