Suppose that a family has

3

children. Also, suppose that the probability of having a girl is

one half 1/2.

Find the probability that the family has the following children.

Exactly

2

girls

and

1

boy

deleted.... see below

You need to consider the order in which they could be born, so the possibilities are:

1st born. 2nd born. 3rd born.

B. B. B

B. B. G

B. G. B

G. B. B

B. G. G

G. B. G

G. G. B

G. G. G

So the probability of exactly 2 girls and 1 boy is 3/8.

P(2 girls) = C(3,2) (1/2)^3 = 3 * (1/8) = 3/8