请教OG13 DS134

jessie201237 · 发表于 2013-10-17 20:56:25

favorable / unfavorable/ not sure
m 40/20/40
n 30/35/35
134. The table above shows the results of a survey of
100 voters who each responded "Favorable" or
"Unfavorable" or "Not Sure" when asked about their
impressions of Candidate Mand 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.

Arithmetic Sets
If* is the number ofvoters who responded
"Favorable" for both candidates, then it follows
from the table that the number ofvoters who
responded "Favorable" to at least one candidate is
40 + 30 - * = 70 - *. This is because 40 + 30
represents the number ofvoters who responded
"Favorable" for Candidate M added to the
number of voters whoresponded "Favorable" for
Candidate N, a calculation that counts twice
each of the * voters who responded "Favorable"
for both candidates.
(1) Given that there were 40 voters who did not
respond "Favorable" for either candidate and
there were 100 voters surveyed, the number
of voters who responded "Favorable" to at
least one candidate is 100 - 40 = 60.(为什么这里可以直接减去就的得出unfavorable的，没有respond favorable的话，不是还有个not sure的吗)
Tierefore, from the comments above, it
follows that 70 - * = 60, and hence * = 10;
SUFFICIENT.
(2) The information given affects only the
numbersof voters in the categories
"Unfavorable" for Candidate M only,
"Unfavorable" for Candidate N only, and
"Unfavorable" for both candidates. Thus,
the numbers of voters in the categories
"Favorable" for CandidateM only,
"Favorable" for Candidate N only, and
"Favorable" for both candidates are not
affected. Sincethese latter categories are
only constrained to have certain integer
values that have a total sum of70 - *, more
than one possibility exists for the value of*.
For example, the numbers of voters in the
categories"Favorable" for Candidate M
only, "Favorable" for Candidate N only,
and "Favorable" for both candidates could
be 25, 15, and 15, respectively, which gives
70 - * = 25 +15 +15, or * = 15. However,
the numbers of voters in the categories
"Favorable" for Candidate M only,
"Favorable" for Candidate N only, and
"Favorable" for both candidates could be
30, 20, and 10, respectively, which gives
70-* = 30 + 20 + 10,or* = 10;NOT
sufficient.-------------（完全看不懂啊，求助各位大大。。）
The correct answer is A;
statement 1 alone is sufficient.

kaylotus · 发表于 2013-10-17 21:27:14

第一个条件的话,因为问的是fav的,所以可以把unfav和not sure的看做一个整体(100-fav),这个整体里两个是个什么情况对fav是没有影响的,所以条件一可以sufficient

第二个不行的原因其实跟第一个可以的原因是差不多的, 第二个条件只告诉了unfav的情况,所以可以推出fav+not sure这个整体是什么情况..但是因为没有not sure的数据所以不能知道fav单独是怎么样的..所以insufficient

jessie201237 · 发表于 2013-10-20 17:28:34

kaylotus 发表于 2013-10-17 21:27
第一个条件的话,因为问的是fav的,所以可以把unfav和not sure的看做一个整体(100-fav),这个整体里两个是个什 ...

第一个， 40个不fav，那就是40里面包括了unfav和not sure的，然后100-40=60至少一个fav的，是这么理解吧，谢谢哈~

请教OG13 DS134

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