A bag contains six 1-dollar bills, three 5-dollar bills, and two 10-dollar bills. An experiment consists of drawing three random bills from the bag simultaneously.

Question

Considering each possible group of three bills as an outcome, the experiment has C(11,3)=165 equally likely outcomes in its sample space. Let event E be that at least two 5-dollar bills were drawn. What is Pr(E)?

Answer 1

This is a problem for the hypergeometric distribution and the answer is

(3*8+1)/165=5/33.

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