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

來源: jinjing 於 2010-05-28 18:28:25 [] [舊帖] [給我悄悄話] 閱讀數 : (206 bytes)

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.

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

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