If a family has two children who are not twins, what is the probability that both are boys? (Assume single boy or girl births are equally likely.)

Multiply the probability that the first child is a boy and the probability that the second child is a boy to obtain \(\frac{\mathrm{1} }{\mathrm{2}} \times \frac{\mathrm{1} }{\mathrm{2}} = \frac{\mathrm{1} }{\mathrm{4}}\)