Multiple choice

John and Janet appear in an interview for two vacancies for the same post. The probability of John’s selection is 1/5 and that of Janet is 1/7. The probability that only one of them will be selected is

  1. 24/1225

  2. 2/7

  3. 346/1225

  4. 2/35

  5. 8/35
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let, P(R) = Probability of John’s selection = 1/5.  So, the probability that John is not selected is P(R ̅) = 1 - 1/5 = 4/5. Similarly, P(A) = Probability of Janet’s selection = 1/7. So, P(A ̅) = 1 - 1/7 = 6/7. Hence, the probability that only one of them will be selected is = P(R) × P(A ̅) + P(A) × P(R ̅) = 2/7.

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