概率难题，大家帮忙啊

yahooww

wut is the probability that a 5 card drawn from  a standard 52-card deck will have 3 queens (1 has to be the queen of spades), and 2 other spades

sinocheetah

First: find out the combination of 3 Q, C(3,2);

Second: find out the combination of the other 2 cards: C(12,2), because you cannot choose from Queens this time.

Third: find out the combination of 5 cards: C(52,5)

Fourth: the possibility is [C(3,2)*C(12,2)]/C(52,5)

[此贴子已经被作者于2006-7-28 15:59:19编辑过]

yahooww

我自己做了，不知道对不对

C（52，1）C（3，2）C（12，2）/C（52，5）

yahooww

以下是引用sinocheetah在2006-7-28 15:49:00的发言：

First: find out the combination of 3 Q, C(3,2);

Second: find out the combination of 5 cards: C(52,5)

Third: the possibility is C(3,2)/C(52,5)

除了3个Q，还有另外2个SPADE来。而且有个Q是指定的。

所以我觉得这个可能不对

sinocheetah

Since there must be one spade queen, we only need to consider the combination of the other four cards.

Pls refer to my revised solution. At first I thought of only 3 cards.

sinocheetah

C(52,1)是没有道理的。

anclewu

C(3, 2)*C(48, 2) / C(52, 5)

bloodymica

以下是引用anclewu在2006-7-28 23:16:00的发言：
C(3, 2)*C(48, 2) / C(52, 5)

就是吗~~这个才对

jandjshi

以下是引用sinocheetah在2006-7-28 15:49:00的发言：

First: find out the combination of 3 Q, C(3,2);

Second: find out the combination of the other 2 cards: C(12,2), because you cannot choose from Queens this time.

Third: find out the combination of 5 cards: C(52,5)

Fourth: the possibility is [C(3,2)*C(12,2)]/C(52,5)

这个才对吧.

楼上那个C(48,2) 不对啊. spade一共才13张, 已知"黑猪"被拿了, 那只有C(12,2)啊.

yahooww

thanks a lot.

我一直觉得52张牌里抽一个SPADE QUEEN是C(52,1)