in Probability
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in Probability
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3 Comments

1/3  ?
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Yes. Please explain with solution
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1 Answer

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Best answer

Let total student = x .

Number of student who think they know the answer  = (20/100)*x = x/5

Number of student who knows correctly = (1/2)*(x/5) = x/10

number of students who knows wrong answer = (1/2)*(x/5) = x/10

Remaining candidate = x-(x/5) = 4x/5

probability of answering correctly by remaining candidate = (1/4)*(4x/5) = x/5 ......[as 1 out of 4 option is correct]

P(answer knew / aswered correctly ) = P(answer knew ∩ answered correctly) / P(answered correctly) 

      =   (x/10) / { (x/10) + (x/5) } = 1/3

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