JEE Main & Advanced Mathematics Probability Question Bank Self Evaluation Test - Probability-II

  • question_answer
    The probability that a particular day in the month of July is a rainy day is ¾. Two person whose credibility are 4/5 and 2/3. Respectively, claim that 15 July was rainy day. The probability that it was really a rainy day is

    A) \[\frac{12}{13}\]

    B) \[\frac{11}{12}\]

    C) \[\frac{24}{25}\]

    D) \[\frac{29}{30}\]

    Correct Answer: C

    Solution :

    [c] Let events A : Event that first man speak truth B: Event that second man speaks truth R: Day is rainy \[\therefore P(A)=\frac{4}{5},P(B)=\frac{2}{3},P(R)=\frac{3}{4}\] \[\therefore \] Required probability \[=\frac{P(A\cap B).P(R)}{P(A\cap B).P(R)+P(A'\cap B,).P(R')}\] \[=\frac{\frac{4}{5}\times \frac{2}{3}\times \frac{3}{4}}{\frac{4}{5}\times \frac{2}{3}\times \frac{1}{5}+\frac{1}{3}\times \frac{1}{4}}=\frac{24}{25}.\]


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