Harry and Tom have each found a 4-digit perfect square, a 3-digit perfect cube and a 3-digit triangular number that use 10 different digits, but with no leading zero. A triangular number is one that ...

Which is 9. So 9 is a square number. Here are some other examples of square numbers. Can you see how all these numbers can be arranged into a square? Which is 64. So 64 is a cube number. Here are some ...