Posted by meep on .
Five boys and seven girls in a history class will go on a field trip during the Easter vacation. They make a committee of three members to prepare for the trip. What is the probability that this committee will consist of three boys? What is the probability that the committee will have two boys and one girl?

math 
Reiny,
number of committes without restriction
= C(12,3) =220
number of committess with three boys
= C(5,3) = 10
prob( 3boys) = 10/220 = 1/22
number of committees with 2 boys, 1 girs
= C(5,2) x C(7,1)
= 70
prob (2boys, 1 girl ) = 70/220 = 7/22