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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

 Apr 11, 2019
 #1
avatar+26675 
+1

deleted.... see below

 Apr 11, 2019
edited by Guest  Apr 11, 2019
 #2
avatar+30921 
+3

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.

 Apr 11, 2019
 #3
avatar+111455 
+1

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

 

cool  cool cool   

 Apr 11, 2019

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