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

The probability that atleast one of the events happens is If probability of thei

The probability that atleast one of the events \( A, B \) happens is \( 0.6 . \) If probability of their simultaneously happening is \( 0.5, \) then \( \boldsymbol{P}(\overline{\boldsymbol{A}})+\boldsymbol{P}(\overline{\boldsymbol{B}})= \)

  • A. 0.4
  • B. 0.8
  • C. 0.9
  • D. 1.

Step-by-step solution

Given P(A∪B)=0.6 and P(A∩B)=0.5. By inclusion-exclusion: P(A∪B)=P(A)+P(B)-P(A∩B) ⇒ 0.6=P(A)+P(B)-0.5 ⇒ P(A)+P(B)=1.1. Then P(Ā)+P(B̄)=(1-P(A))+(1-P(B))=2-(P(A)+P(B))=2-1.1=0.9.
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