概率 英文的

题目

概率 英文的
36个人来自于两个家庭.其中25个姓李,11个姓陈.25个李姓人中,有4个单身男,5个单身女,和8对新人.11个陈姓认中,2个单身男,3个单身女,和3对新人.从中选出两个人.
1.find the probability that they are married to each other.
2.find the probability that they both have named Lee,given that they are married to each other.
3.find the probability that they are a man and a women with the same name.
4.find the probability that they are married to each other,given that they are a man and a woman with the same name.

答案

1.find the probability that they are married to each other.
==[(C1--8）+(C1--3）]/(C2--36)=11/(36*35/2)=11/630;
2.find the probability that they both have named Lee,given that they are married to each other.
===(C1--8)/(C2--36)=8/(36*35/2)=4/315;
3.find the probability that they are a man and a women with the same name.
=【{[C1--4]*[C1--5]+8}+{[C1--2]*[C1--3]+3}】/(C2-36)
=[20+8+6+3]/(36*35/2)=37/630;
4.find the probability that they are married to each other,given that they are a man and a woman with the same name.
P of lee=[C1--8]/(C2-25)=8/(25*24/2)=2/75;
P of chen=[C1--3]/(C2-11)=3/(11*10/2)=3/55;
####