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The chance of a student passing an exam is 20%. The chance of a student passing the exam and getting above 90% marks in it is 5%, Given that a student passes the examination, the probability that the student gets above 90% marks is
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1 18
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1 4
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2 9
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5 18
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Correct Option: B
Given that the student is passing exam, i.e., if only 20 students (out of 100) are considered, of the 5 students get more than 90%
∴ 5 out of 20 is the probability or 1/4 is the answer.
Alternative Method :
Let the student pass the examination be A and student pass the examination and got about 90% marks be B Now P(A) = 20% and P(A ∩ B) = 5%
| ∴ P |  |  | = | = | = | ||||
| A | P(A) | 20% | 4 |
