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Jeff decides to play with a Magic 8 Ball. Each time he asks it a question, it has a 2/5 chance of giving him a positive answer. If he asks it 5 questions, what is the probability that it gives him exactly 2 positive answers? Express your answer as a fraction.

Guest Aug 1, 2017
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The probability of two correct out of five is (2/5)2(3/5)3 → 108/3125

 

However, there are 5C2 → 10 ways of choosing 2 from 5, so overall the probability is 10*108/3125 → 216/625

Alan  Aug 2, 2017

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