There are 14 counters in a bag. 7 of the counters are red. 4 of the counters are blue. 3 of the counters are green. Billie takes two counters at random from the bag.
Work out the probability that both of the counters Billie 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.