求教GWD-27

saiever

这题应该如何考虑？

如何考虑集合间的交叉？

Q33:

 

	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.

Answer: A

chianalin

畫看看樹狀圖  應該比較好理解

SPARTAN_117

方便起见，定义简写如下：F(Favorable), UF(Unfavorable), NS(Not Sure)，先看（1）：说有40人对M和N都不F，也就是说这40人对M和N不是UF就是NS。于是看表格最右面两列：100选民中对M持UF或NS的有60人，对N持UF或NS的有70人。

根据（1），这两组人中有40人同时对M和N不F，就是说两组人交集的人数是40，因而第一组60人中剩下的20人只可能支持N；第二组70人中必然有30人支持M。从而20+30=50人只支持某一方，加上前面两个都不支持的40人，总共90人，取补集——剩下那10个就是双方都支持的。所以（1）充分。

用同样的思路去解（2），会发现F和NS混在一起没有进一步信息区分彼此，由于题目问的是F，从而（2）不充分。最后答A

liubin1987

这道题也有讨论帖的,你去搜下可以找的到.