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進階教學(14)—-紅白黑3色球,紅球先取完
袋中有紅球4個、白球3個、黑球5個,且每個球被取到機率相等, 今每次取出一球不放回袋中,連續取球,則紅球先取完的機率為?
P(紅球先取完)
=P(在最後一球為白球的條件下,紅球比黑球先取完)+
P(在最後一球為黑球的條件下,紅球比白球先取完)
得答案為