For those of you revising for Paper 2 and 3 GCSE Maths then this site is a must. You will find predicted papers that have been carefully written considering what topics have already been tested in Paper 1. You get immediate feedback on your answers and can see what grade you would potentially get if you do the same in the real exam. If you get stuck there are video explanations of each question. A great way to revise.
Here is the solution.
The solution to the “How many triangles?” puzzle.