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    Question

    Arun tells the truth in 70% of cases and Varun tells the

    truth in 50% of cases. Find the probability that at least one of them tells the truth in a given situation.
    A 17/20 Correct Answer Incorrect Answer
    B 12/11 Correct Answer Incorrect Answer
    C 15/17 Correct Answer Incorrect Answer
    D 20/21 Correct Answer Incorrect Answer

    Solution

    ATQ,

    Arun tells truth = 0.7

    → lies = 0.3

    Varun tells truth = 0.5

    → lies = 0.5

    At least one truth:

    P = 1 – P(both lies)

    P(both lies) = 0.3 Ă— 0.5 = 0.15

    P(at least one truth) = 1 – 0.15 = 0.85 = 17/20

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