一道GRE摸球的概率题

来源：百度知道 编辑：UC知道 时间：2024/05/16 07:32:04
three red marbles and 2 white marbles are placed in an empty box. One marble at a time is to be selected randomly and removed from the box until all 5 marbles have been removed. What is the probability that each of the first 3 marbles removed will be red.

我是C(3,1)×C(2,1)/C(5,1)×C(4,1)×C(3,1)×C(2,1)=1/20
答案是1/10=3/5×2/4×1/3

答案是正确的。每次只抽一个，所以不要考虑白球，你的C（2，1）我不知道为什么要加进去。
第一个为红球概率，3/5，第二个，2/4，第三个1/3。独立事件概率相乘即可