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There are 3 math clubs in the school district, with 5, 7, and 8 students respectively. Each club has two co-presidents. If I randomly select a club, and then randomly select three members of that club to give a copy of Introduction to Counting and Probability, what is the probability that two of the people who receive books are co-presidents?

 Apr 4, 2021
 #1
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For the first math club, there is a 3/5 probability that two of the people that receive books are co-presidents.

For the second math club, there is a 1/7 probability that two of the people that receive books are co-presidents.

For the third math club, there is a 3/28 probability that two of the people that receive books are co-presidents.

 

The final answer is then (3/5 + 1/7 + 3/28)/3 = 17/60.

 Apr 4, 2021
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Sorry, it was incorrect, but I have one more try.

RiemannIntegralzzz  Apr 4, 2021

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