14) The percentage of females born in twin births is $48.5\%$. Assuming that in twin births the probability that the two newborns are of different sexes is $33\%$, what is the probability that in a twin birth two females are born?
(A) $32\%$
(B) $33\%$
(C) $33.33\%$
(D) $35\%$
(E) $50\%$.
14) The answer is $\mathbf{( A )}$. Let $p \%$ be the probability that in a twin birth, two females are born. It follows that out of 100 twin births, $33+2 p$ females are born, resulting in a female percentage of $(33+2 p) / 200=(16.5+p) \%$. Since this must be $48.5 \%$, we get $p=32$.