题目内容
某校组织一次冬令营活动,有8名同学参加,其中有5名男同学,3名女同学,为了活动的需要,要从这8名同学中随机抽取3名同学去执行一项特殊任务,记其中有X名男同学.
(1)求X的分布列;
(2)求去执行任务的同学中有男有女的概率.
(1)求X的分布列;
(2)求去执行任务的同学中有男有女的概率.
(1) X的分布列为
(2)![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042119021476.png)
X | 0 | 1 | 2 | 3 |
P | ![]() | ![]() | ![]() | ![]() |
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042119021476.png)
解:(1)X的可能取值为0,1,2,3.
P(X=0)=
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042119036515.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042118958403.png)
P(X=1)=
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042119067672.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042118958445.png)
P(X=2)=
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042119114677.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042118974495.png)
P(X=3)=
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042119036515.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042118989461.png)
即X的分布列为
X | 0 | 1 | 2 | 3 |
P | ![]() | ![]() | ![]() | ![]() |
P(X=1)+P(X=2)=
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042118958445.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042118974495.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824042119021476.png)
![](http://thumb.zyjl.cn/images/loading.gif)
练习册系列答案
相关题目