This is my solution to https://nrich.maths.org/13377 'cause maths. Problem Ash, Si, Sami and Mani are playing a game. Each of them writes down a statement that describes a set of numbers. Ash writes "Multiples of five". Si writes "Triangular numbers". Sami writes "Even, but not multiples of four". Mani writes "Multiples of three but not multiples of nine". Can you find some two-digit numbers that belong in two of the sets? (coming soon) Can you find some two-digit numbers that belong in three sets? (also coming soon) What is the smallest number that belongs in all four sets? 210
