Question 1039899
B = child is a boy
G = child is a girl


P(B) = 1/2 = 0.5
P(G) = 1/2 = 0.5


Because the events are independent, ie the gender of child1 doesn't affect the gender of child2 or child3, this means


P(3 girls) = P(girl and girl and girl)
P(3 girls) = P(girl)*P(girl)*P(girl)
P(3 girls) = P(G)*P(G)*P(G)
P(3 girls) = 0.5*0.5*0.5
P(3 girls) = <font color=red size=5>0.125</font>