If you don't know the order the answer is 1/3

來源: 於 2010-05-28 18:28:25 [舊帖] [給我悄悄話] 本文已被閱讀：次

If you know first (or second) is boy,the answer is 1/2.
If you don't know the order is 1/3.
Sorry ,I didn't see Qn clearly.
The second Qn is condition Prob.
P(E/F)=P(E&F)/P(F)=(1/4)/(3/4)=1/3.