Mathematics 4024 · O Level · Probability of combined events
Probability of combined events — practice question
A bag holds 5 balls, with 3 red balls and 2 blue balls. A ball is chosen at random from the bag and is not put back. If that ball is red, a second ball is then chosen at random from the bag and is not put back. This continues until a blue ball is drawn from the bag.
(a)[2]
Finish the tree diagram.
(b(i))[1]
Write each answer as a fraction, then find the probability that the second ball taken is blue.
(b(ii))[2]
Write each answer as a fraction, then find the probability that a blue ball is the second, or the third, ball taken.
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Accurate branches for the third and fourth balls” …