GMAT 逻辑分析题 (2)

bontakuner

The price of a full-fare flight ticket from Beijing to Shanghai on Air China is the same today as it was a year ago, if inflation is taken into account by calculating prices in constant RMB. However, today 80% of the Beijing-to-Shanghai flight tickets that Air China sells are discount flight tickets and only 20% are full-fare flight tickets, whereas a year ago half were discount flight tickets and half were full-fare flight tickets. Therefore on average, people pay less today in constant dollars for an Air China Beijing-Shanghai flight ticket than they did a year ago.

Which one of the following, if assumed, would allow the conclusion above to be properly drawn?

A) A Beijing-to-Shanghai full fare flight ticket on Air China provides ticket-holders with a lower level of service today than such a ticket provided a year ago.

B) The average number of coach passengers per flight that Air China carries from Beijing to Shanghai today is higher than the average number per flight a year ago.

C) All full fare flight tickets on Air China cost the same in constant dollar RMB as they did a year ago.

D) A Beijing-to-Shanghai discount flight ticket on Air China costs about the same amount in constant dollars today as it did a year ago.

E) The criteria that Air China uses for permitting passengers to buy discount flight tickets on the Beijing-to-Shanghai route are different today than they were a year ago

EvaCheng

D吧。ABE显然都不对，C和D我看了好久以为没区别，最后突然想如果C能
够用那么短的文字表达同样的意思，D还要说那么多废话干吗，这才发现有
个ALL，C的范围太大了，是充分条件，但不是必要条件，所以不是
ASSUMPTION。
sdcar2010你发的问题很有意思，在哪里找的？还有我很佩服你可以用纯英
文那么简洁清晰地讨论逻辑题。

bontakuner

well done!

(C) actually is simply repeating what the stimulus says in the first sentence.

(D), as you just said, is a necessary assumption.  If today's discount is only 1% off the full fare while the discount last year was 99% off the full fare, the conclusion would be totally wrong.

A1  (D), as you just said, is a necessary assumption.  If today's discount is only 1% off the full fare while the discount last year was 99% off the full fare, the conclusion would be totally wrong.
我想的有点不同，选项里的意思应该是去年和今年的打折机票是一个价。而不是说今年的折扣和去年的折扣量是一样的。前提和结论之间的GAP应该是RMB和DOLLARS，第一句话已经说了用RMB衡量的价格一样，结论要美元，那应该是要求汇率稳定，至少美元买的机票价钱没变。不过你说的折扣量似乎也很重要。

bontakuner

Oops, the dollar should be changed to RMB.  My bad.  Considering the existence of the typo, you DO have point to eliminate C according to the difference between RMB and dollar.

I will change the answer C right away.

felixroman

dear sdcar2010, as you said, one of the prompts for sufficient assumptions is: the author's conclusion would be properly drawn if which one of the following was true?  i believe this sentence is similar with the question above:Which one of the following, if assumed, would allow the conclusion above to be properly drawn?
so, why the correct answer we are looking for should be a necessary assumption but not a sufficient one? because the text has already given another necessary assumption:The price of a full-fare flight ticket from Beijing to Shanghai on Air China is the same today as it was a year ago, and the combination of (D) and this one is both sufficient and necessary for the conclusion?

bontakuner

Good catch. D) in fact, is not a necessary assumption, but a sufficient one. A necessary condition would be: Last year'd discount price was not drastically lower than that of this year.

matchMichelle

原来是C 的范围太大了，这里只要北京到上海， D的话我有个疑问，就是如何保证票子的原价是一样的？ 还是说题目的第一句已经提到全票价是一样的，所以可以不提？

A) A Beijing-to-Shanghai full fare flight ticket on Air China provides ticket-holders with a lower level of service today than such a ticket provided a year ago. -------------- not mentioned

B) The average number of coach passengers per flight that Air China carries from Beijing to Shanghai today is higher than the average number per flight a year ago. ---------------- irrelevant

C) All full fare flight tickets on Air China cost the same in constant dollar RMB as they did a year ago.
-------------- constant cost, correct， 我错了，范围太大
D) A Beijing-to-Shanghai discount flight ticket on Air China costs about the same amount in constant dollars today as it did a year ago. ----------------- don’t know the origin cost  这个是正确答案

E) The criteria that Air China uses for permitting passengers to buy discount flight tickets on the Beijing-to-Shanghai route are different today than they were a year ago -------------- irrelevant

cher6068

xx