Two bags, A A\,A and BBB, contain red, green and yellow counters. Bag A A\,A contains 3 red, 2 green and k k\,k yellow, where k k\,k is a positive integer. Bag B B\,B contains 5 red, 4 green and 1 yellow. Taylor picks one counter at random from bag A A\,A and places it into bag BBB. She then picks one counter at random from bag BBB.
Draw a tree diagram to represent this information.
Find, in terms of kkk, the probability that Taylor picks two counters of the same colour.
Given that both counters are the same colour, find, in terms of kkk, the probability they are both yellow.
368 exam-style questions on Edexcel A Level Maths Conditional Probability, covering 2.1 Set Notation, 2.2 Conditional Probability, 2.3 Conditional Probabilities in Venn Diagrams, 2.4 Probability Formulae, and 2.5 Tree Diagrams. Each one has a worked solution and a mark scheme showing where the marks go.