Box A has $7$ red balls and $1$ blue ball. Box B has $9$ red balls and $5$ blue balls. One ball is taken at random from box A and placed into box B. Then a ball is taken at random from box B. The tree diagram below shows the possible colours of the balls selected.
(a)[3]
Complete the tree diagram by showing the probabilities.
(b)[2]
Find the probability that the two balls selected are not the same colour.
(c)[4]
Find the probability that the ball selected from box A is blue, given that the ball selected from box B is blue.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Accurate probabilities for Box A.” …