两题GWD 实在找不到答案 求NN解答

caijilei

GWD9-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.

Answer:

这题答案说是A 但是知道A中的信息根本不能知道有哪些人选not sure啊 求解

GWD9-36

If x, y, and k are positive numbers such that [x/(x+y)](10) +[x/(x+y)] (20) = k and if x < y, which of thefollowing could be the value of k?

A.   10

B.    12

C.    15

D.   18

E.    30

两个空格里面都是x/(x+y) 谢大家！

lhz910216

1
条件说有40个人呢既没有给M好评，有没有给N好评，然后看表
M对应的差评和not sure加起来是60，那这60人里面肯定包含这40了，那么剩下的20人显然是在点评N时，给了好评，否则就不符合条件了。所以给N好评的30人里面有20人是没有给M好评的，所以，30人里剩下的10人就是既给M好评，又给N好评的了

2
这道题我做的时候也没多想，想着x+y凑成个5就可以约去，所以就试试什么x=2,y=3/x=1,y=4，结果就算出来

lucyhou

第二个答案是a吗？

caijilei

lucyhou 发表于 2013-8-13 23:20
第二个答案是a吗？

第二题答案是E

caijilei

lhz910216 发表于 2013-8-13 23:00
1
条件说有40个人呢既没有给M好评，有没有给N好评，然后看表
M对应的差评和not sure加起来是60，那这60人里 ...

发现把题目打错了 应该是 [x/(x+y)](10) +[y/(x+y)] (20) = k 然后我觉得可以变成(10x+20y)/(x+y)=k 然后可以进一步化为10x+20y=k(x+y) 求解这个想法对不对的 为什么你觉得把x+y凑成5就可以约去啊

lhz910216

caijilei 发表于 2013-8-14 14:17
发现把题目打错了 应该是 [x/(x+y)](10) +[y/(x+y)] (20) = k 然后我觉得可以变成(10x+20y)/(x+y)=k 然后 ...

因为K是正整数啊，最简单的就是把分母约去，就算了，当然这不是通用方法了
你这方法对啊10x + 20y =k(x+y)
这样的话如果k=10肯定右边太小，k=20肯定右边太大，所以k在10-20之间，而又x<y，所以k〉15，得出来18啊