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This problem was a little more difficult that it looked, I think.

We had some suggestions that the three groups should be right-angled triangles, equilateral triangles and isosceles triangles. I'm not sure that any of the triangles are equilateral. How do I know?

Emily from said St James School told us:

I think that these triangles are sorted into right-angled scalene, right-angled isosceles and non-right-angled isosceles.
There are no equilateral triangles because they do not ever have any right angles and none of those triangles had the same sides and angles.

You're right, Emily, thank you. Beatrice from Raffles Girls' School in Singapore sent in a picture of the completed groups:


beatrice's solution

Cong, from St Peter's RC Primary also sent us an image of his solution:



cong's solution

I think that each one of you has put just one triangle in the wrong place. I wonder whether you can spot which one it is in each picture?

Well done all of you!