2025 JPJC P2 Q9

2025 JPJC P2 Q9

9 marks

The events \(A\) and \(B\) are such that \(\mathrm{P}(B) = \frac{1}{3}\), \(\mathrm{P}(A|B) = \frac{2}{5}\) and \(\mathrm{P}(A \cup B) = \frac{3}{5}\).

  1. Find \(\mathrm{P}(A)\) and hence, determine whether events \(A\) and \(B\) are independent.[4]
  2. Find the exact value of \(\mathrm{P}(A' \cap B)\).[1]

For a third event \(C\), it is given that \(\mathrm{P}(C) = \frac{1}{2}\) and that \(A\) and \(C\) are mutually exclusive.

  1. Find exactly the greatest and least possible values of \(\mathrm{P}(B' \cap C)\).[4]

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Answer:(a) \(\mathrm P(A)=\dfrac25\), and \(A\) and \(B\) are independent (b) \(\mathrm P(A'\cap B)=\dfrac15\) (c) Least \(\dfrac3{10}\), greatest \(\dfrac25\)

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