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Tangram Paradox

How can the same pieces of the tangram make this bowl before and after it was chipped? Use the interactivity to try and work out what is going on!

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Teddy Town

There are nine teddies in Teddy Town - three red, three blue and three yellow. There are also nine houses, three of each colour. Can you put them on the map of Teddy Town according to the rules?

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Four Triangles Puzzle

Cut four triangles from a square as shown in the picture. How many different shapes can you make by fitting the four triangles back together?


Age 7 to 14 Challenge Level:

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.

Full Screen Version