NO.PZ2015120604000176
问题如下：
Assume :P(event A occurs)=15%, P(event B occurs)=35%, and P(event C occurs)=20%. If the event A, B and C are all independent, what is the P(event A or event C occurs)?
选项：
A.35%.
B.32%.
C.55%.
解释：
B is correct.
Event A, B and C are independent ,
so P(event A or event C occurs)=P(event A occurs)+ P(event C occurs)- P(both event A and event C occur)=15%+20%-15%*20%=32%
如题。
问的是A or C。
如果说一个袋子里有红、蓝、黑，三色球，规则是抽到黑或红都可以获奖
为什么抽到黑+红就不满足规则了.... 不应该是包含的状况吗？为什么要减去？
