题目
题型:不详难度:来源:
(1)求这3人所在学院的编号恰好成等比数列的概率;
(2)求这3人中中英文讲解员人数的分布列及数学期望。
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014004-29579.jpg)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-11315.gif)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
![]() | 0 | 1 | 2 | 3 |
![]() | ![]() | ![]() | ![]() | ![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014007-27823.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014007-60681.gif)
解析
“这3人都来自1号学院”记为事件A1,
“这3人都来自2号学院”记为事件A2,
“这3人分别来自1号、2号、4号学院”记为事件A3,
∴P(A1)=P(A2)=
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014007-66161.gif)
P(A3)=" "
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014007-12647.gif)
∴P(A)= P(A1)+P(A2)+P(A3)=
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-11315.gif)
∴这3人所在学院的编号恰好成等比数列的概率是
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-11315.gif)
(2)设这3人中中英文讲解员的人数为
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
P(
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014007-38369.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014008-77242.gif)
P(
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014008-35450.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014008-12888.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
![]() | 0 | 1 | 2 | 3 |
![]() | ![]() | ![]() | ![]() | ![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014005-20469.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014008-27678.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030014007-60681.gif)
核心考点
试题【(本小题满分12分)上海世博会举办时间为2010年5月1日~10月31日。福建馆以“海西”为参博核心元素,主题为“潮涌海西,魅力福建”。福建馆招募了60名志愿者】;主要考察你对离散型随机变量均值与方差等知识点的理解。[详细]
举一反三
(1)若三人中每个人可以选择任一球队,且选择各个球队是等可能的,求四支球队中恰好有两支球队有人选择的概率;
(2)若三人中有一名女球迷,假设女球迷选择巴西队的概率为
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030013950-41387.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191030/20191030013950-73537.gif)