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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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