sana.noor wrote:Alfonso is conducting a survey of families with 3 children. If a family is selected at random, what is the probability that the family will have exactly 2 boys if the second child is a boy?
a)3/8
b)4/8
c)1/2
d)1/4
e)2/8
C
Since good outcomes are BBG and GBB, what matters here is the gender of the THIRD child.
If the first child is a boy, then the third child must be a girl.
If the first child is a girl, then the third child must be a boy.
In other words, the gender of the third child must be DIFFERENT from that of the first child.
P(gender of the third child is different from that of the first child) = 1/2.
The correct answer is
C.
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