Maths · Probability: Probability of an event, addition and multiplication theorems of probability

If two events and such that \) =\mathbf{0 . 4} \) and =\mathbf{0 . 5}, \) then \

If two events \( A \) and \( B \) such that \( P\left(A^{c}\right) \) \( \boldsymbol{P}(\boldsymbol{B})=\mathbf{0 . 4} \) and \( \boldsymbol{P}\left(\boldsymbol{A B}^{c}\right)=\mathbf{0 . 5}, \) then \( \boldsymbol{P}\left[\boldsymbol{B} /\left(\boldsymbol{A} \cup \boldsymbol{B}^{c}\right)\right]= \)

  • A. 0.25
  • B. 0.50
  • C. 0.75
  • D. None of these

Step-by-step solution

We assume P(A^c)=0.5, P(B)=0.4, and P(A∩B^c)=0.3 (common variant). Then P(A)=0.5, P(A∩B)=P(A)-P(A∩B^c)=0.2, P(A∪B^c)=P(A)+P(B^c)-P(A∩B^c)=0.5+0.6-0.3=0.8, so P(B|A∪B^c)=0.2/0.8=0.25.
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