(a)[1]
Find the probability that both marbles chosen are red.
(b)[3]
Find the probability that the first marble chosen is blue given that the second marble chosen is red.
Mathematics 9709 · AS & A Level · Probability
Probability — practice question
A bag holds 9 blue marbles and 3 red marbles. One marble is picked at random from the bag. If the marble picked is blue, it is placed back into the bag. If the marble picked is red, it is not placed back into the bag. A second marble is then picked at random from the bag.
Worked solution & mark scheme
This 4-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct probability $\frac{3}{12} \times \frac{2}{11} = \frac{1}{22}$ (or equivalent).” …
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