Suppose that a family has exactly n children (n ≥ 2).
Assume that the probability that any child will be a girl is ½ and that all births are independant.
Given that the family has at least one girl,
determine the probability that the family has at least one boy.
Bayes' Theorem: .
The opposite of "at least boy and at least girl" is "no boys or no girls."
. . . Hence: .
The opposite of "at least one girl" is "no girls".