百度作业网一道GRE摸球的概率题
来源：学生作业帮 编辑：百度作业网作业帮 分类：英语作业 时间：2024/05/13 17:04:30
一道GRE摸球的概率题
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
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
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