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MHT CET202618 April 2026Evening ShiftMathematicsProbabilityActual

In an entrance test, there are multiple choice questions. There are four possible answers to each question, only one of which is correct. The probability that a student knows the answer to a question is 90%. If he gets the correct answer to a question, then the probability that he was guessing is

Options

  1. A37 40
  2. B1 37
  3. C36 37
  4. D1 9

Correct answer

B. 1 37

Step-by-step solution

Let E₁ be the event that the student knows the answer and E₂ be the event that the student guesses the answer. P(E₁) = 90 100 = 9 10 P(E₂) = 1 - P(E₁) = 1 10 Let A be the event that the student gets the correct answer. If the student knows the answer, the probability of getting it correct is 1 , so P(A|E₁) = 1 . If the student guesses, since there are 4 options and only 1 is correct, the probability of getting it correct is 1 4 , so P(A|E₂) = 1 4 . By Bayes' theorem, the probability that the student was guessing gi

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