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    Question

    There are three people – Axe, Wye and Zed. Probability that Axe speaks the truth is 7/20, probability that Wye speaks the truth is 3/5 and probability that Zed speaks truth is 5/6. For a particular question asked, at most 2 people speak truth. All people answer to a particular question asked.

    Axe speaks truth only when Wye does not speak truth,

    then what is the probability that Zed does not speak truth on a question?
    A 53/600 Correct Answer Incorrect Answer
    B 47/800 Correct Answer Incorrect Answer
    C 16/95 Correct Answer Incorrect Answer
    D 43/800 Correct Answer Incorrect Answer
    E 55/728 Correct Answer Incorrect Answer

    Solution

    Case (1) : Wye does not speak truth  So, Axe speaks truth here Probability that Zed does not speaks truth = 7/20  ×(1-3/5)×(1-5/6) = 7/300 Case (2) : Wye speaks truth  So, Axe does not speaks truth here Probability that Zed does not speaks truth = (1-7/20)×  3/5  ×(1-5/6) = 13/200 Required Probability = 7/300+  13/200 = 53/600

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