There are 15 socks in a drawer. 7 of the socks are black, 5 of the socks are navy, and 3 of the socks are grey. James takes two socks at random from the drawer.
Work out the probability that both of the socks James takes are the same colour.
You must show your working.
72 exam-style questions on OCR GCSE Maths Conditional Probability. Each one has a worked solution and a mark scheme showing where the marks go.