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COMEDK · Maths · 36. Probability

A student answers a multiple choice question with 5 alternatives, of which exactly one is correct. The probability that he knows the correct answer is \(p, 0 < p < 1\). If he does not know the correct answer, he randomly ticks one answer. Given that he has answered the question correctly, the probability that he did not tick the answer randomly, is

  1. A \(\dfrac{3 p}{4 p+3}\)
  2. B \(\dfrac{5 p}{3 p+2}\)
  3. C \(\dfrac{5 p}{4 p+1}\)
  4. D \(\dfrac{4 p}{3 p+1}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\dfrac{5 p}{4 p+1}\)

Step-by-step Solution

Detailed explanation

Let \(K\) be the event that the student knows the correct answer, and \(R\) be the event that the student ticks the answer randomly. Let \(C\) be the event that the student answers the question correctly. The probability that the student knows the answer is \(P(K) = p\). The…