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

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.

所有跟帖： 

• If m boys and n girls,answer is (m-1)/(m+n-1) -jinjing- ♀ (42 bytes) () 05/30/2010 postreply 08:35:27