GWD数学9-20

lenaie520

Q20:

    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.
答案是A
完全不懂，求解。。。

Betty1989

我也不懂……

linchaoyi

这个好像是这样子的。一共100个人
m40 （20 40)
n 30   (35 35)
可以把括号里的看成是一起的，这些人没有给M或N好评。即100人里有60人没有给M好评，70人没给N好评。
而60人里有40人也没给N好评，那么剩下的20人就是给N好评的。那么就可以知道给N好评没有给M好评的人是20人
而给N好评的只有两种人，给N不给M，或者都给好评了。所以可以知道给M和N好评的有10个人。所以（1）充分。

而B只给出了都给Unfavourable的人数，无法确定给好评或者不确定的人数，所以（2）不充分，选A