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A student is presented in the exam knowing 85 questions of 100 possible questions. In the exam, randomly, three questions are withdrawn. Find the probability of the event A: "the student will know the three questions withdrawn".

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closed as off-topic by Lee David Chung Lin, man and laptop, Leucippus, user3658307, Eevee Trainer Apr 23 at 4:16

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If God help him the first question will be among the 85 he does know, the second in 84 and last in 83 the probability will be: $\mathbb{P}(A)=\frac{85}{100}\times\frac{84}{99}\times\frac{83}{98}$

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