In answering a question on a multiple choice test, a student either knows the answer or guesses. Let `3/4` be the probability that he knows the answer and `1/4` be the probability that he guesses. Assuming that a student who guesses at the ans

Explanation

Probablity student knows the answer, `P(A) = 3/4`

Probablity student knows the answer, `P(B) = 1/4`

Probablity of correct answer when student knows the answer,
`P(C/A)= 1`

Probablity of correct answer when student guesses the answer,
`P(C/B)= 1/4`

So, probablity student gives answer correctly, when he knows the answer,

`P(A/C) = (P(A)*P(C/A))/(P(A)*P(C/A))+(P(B)*P(C/B))`

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