InterviewSolution
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InterviewSolution
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In an entrance test, there are multiple choicequestions. There are four possible answers to each question, of which one iscorrect. The probability that a student knows the answer to a question is90%. If the gets the correct answer to a question, then find the probabilitythat he was guessing.A. `(1)/(9)`B. `(36)/(37)`C. `(1)/(37)`D. `(37)/(40)` |
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Answer» Correct Answer - C Consider the following events : `E_(1) to ` He knows the answer, `E_(2) to `He guesses the answer `A to ` He gets the correct answer. We have, `P(E_(1))=(90)/(100)=(9)/(10),P(E_(2))=(1)/(10)`, `P(A//E_(1))=1, P(A//E_(2))=(1)/(4)` `therefore` Required probability `=P(E_(2)//A)` `=(P(E_(2))P(A//E_(2)))/(P(E_(1))P(A//E_(1))+P(E_(2))P(A//E_(2)))` `=((1)/(10)xx(1)/(4))/((9)/(10)xx1+(1)/(10)xx(1)/(4))=(1)/(37)` |
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