CAIE S1 2021 November — Question 7

Exam BoardCAIE
ModuleS1 (Statistics 1)
Year2021
SessionNovember
TopicConditional Probability
TypeSampling without replacement from bags/boxes

7 Box \(A\) contains 6 red balls and 4 blue balls. Box \(B\) contains \(x\) red balls and 9 blue balls. A ball is chosen at random from box \(A\) and placed in box \(B\). A ball is then chosen at random from box \(B\).
  1. Complete the tree diagram below, giving the remaining four probabilities in terms of \(x\).
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  2. Show that the probability that both balls chosen are blue is \(\frac { 4 } { x + 10 }\).
    It is given that the probability that both balls chosen are blue is \(\frac { 1 } { 6 }\).
  3. Find the probability, correct to 3 significant figures, that the ball chosen from box \(A\) is red given that the ball chosen from box \(B\) is red.
    If you use the following lined page to complete the answer(s) to any question(s), the question number(s) must be clearly shown.