Question 729338
There is only one way to choose billy and lock him into slot 1


There are 4 C 3 = 4 ways to choose 3 girls (for the remaining three slots)


So there are 1*4 = 4 ways to pick a committee with Billy as the only boy.


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There are 7 C 4 = 35 ways to pick a committee in all. So the probability to pick a committee with Billy as the only boy is <font color="red">4/35</font> which in decimal form is <font color="red">0.11428571428571</font>