请教 GWD 9-23(无重复版本)

4mmgirl

                               favorable        unfavorable    not sure
candidate M               40                      20                40
candidate N               30                     35                  35


The table above shows the results of a survey of 100 voters each responded "favorable" or "unfavorable" or "not sure" when asked about their impressions of candidate M and of candidate N.  What was the number of voters who responded "favorable" for both candidates?

    

(1)   The number of voters who did not respond "favorable" for either candidate was 40.

    

(2)     The number of voters who responded "unfavorable" for both candidates was 10.

[此贴子已经被作者于2009/9/22 11:00:05编辑过]

sysxy1987

答案是不是A啊？不是很确定。

cllcchocolat

偶也觉得是A...

1)用P(A+B)=P(A)+P(B)-P(AB),这里是求P(AB)=40+30-(100-40)=10 (这里概率和数字一样)

用2)求不出的吧,有没有NN确认一下答案

4mmgirl

答案是A

4mmgirl

谢谢各位！