求教GWD31-09-20

ConnieC

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.
    
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

问一下这道题改怎么解答?

如果遇到这类题又该怎么解答？

ConnieC

把unfavorable和not sure合并为not favorable
                   Favorable   not favorable
Candidate M    40                60
Candidate N    30                70

根据条件1, 在not favorable里都减去40人变成
          Favorable   not favorable
Candidate M    40               20
Candidate N    30                30

这时只有3种人存在: 选Favor M+Favor N的,  选Favor M+not favor N的, 选not favor M+favor N的
发现那20个not favor M的人必然选了Favor N...同理30个not favor N的人必然选了favor M...
所以都剪掉之后还剩下10个人两个都favor...

条件2单独用做不出来...选A

-- by 会员 liyingcai1988 (2010/7/25 1:00:20)

哇~谢谢~豁然开朗

liyingcai1988

把unfavorable和not sure合并为not favorable
                   Favorable   not favorable
Candidate M    40                60
Candidate N    30                70

根据条件1, 在not favorable里都减去40人变成
          Favorable   not favorable
Candidate M    40               20
Candidate N    30                30

这时只有3种人存在: 选Favor M+Favor N的,  选Favor M+not favor N的, 选not favor M+favor N的
发现那20个not favor M的人必然选了Favor N...同理30个not favor N的人必然选了favor M...
所以都剪掉之后还剩下10个人两个都favor...

条件2单独用做不出来...选A

ConnieC

自己顶