Question

It is observed that 1 triangle can be found in the 1st figure, 3 triangles in the 2nd figure, 6 triangles in the 3rd figure, and so on. John claims that more than 100 triangles can be found in the 15th figure? Do you agree? Explain your answer.

Answer 1

well, the nth figure has n(n+1)/2 triangles, so check it out.