这道题想了很久 并不觉得C是扩大范围或者无关 个人的愚见
29. The price of a full-fare coach ticket from Toronto to Dallas on Breezeway Airlines is the same today as it was a year ago, if inflation is taken into account by calculating prices in constant dollars. However, today 90 percent of the Toronto-to-Dallas coach tickets that Breezeway sells are discount tickets and only 10 percent are full-fare tickets, whereas a year ago half were discount tickets and half were full-fare tickets. Therefore, on average, people pay less today in constant dollars for a Breezeway Toronto-to-Dallas coach ticket than they did a year ago.
Which one of the following, if assumed, would allow the conclusion above to be properly drawn?
看到on average要想到人数的
Full-fare今年和去年是相等的 那就都用F 然后D是今年的discount价格 d是去年的discount价格 n和m分别是票的数量
今年的平均票价: (90%n*D+10%n*F)/n 那么去年的平均票价: (50%m*d+50%m*F)/m
从选项出发 选能够满足的选项 例如B如果D=d 那么就有0.9D+0.1F=0.5D+0.1F+0.4D=0.5d+(0.1F+0.4d)<0.5d+(0.1F+0.4F) 其中F>D而且F>d 因为全票价毕竟比打折票价要高啊
full fare是一样的，去年一半是打折票，今年90％是打折票，要得出人们付的平均票价钱少了，那么assumption，就是今年打折票的价钱和去年一样。
(A) A Toronto-to-Dallas full-fare coach ticket on Breezeway Airlines provides ticket-holders with a lower level of service today than such a ticket provided a year ago. 无关
(B) A Toronto-to-Dallas discount coach ticket on Breezeway Airlines costs about the same in constant dollars as they did a year ago.
(C) All full-fare coach tickets on Breezeway Airlines cost the same in constant dollars as they did a year ago. 这个选项说的似乎 10%n*F=50%mF 但是不知道D与d 还有n与m的关系 所以无法确定两个平均值谁大谁小
(D) The average number of coach passengers per flight that Breezeway Airlines carries from Toronto to Dallas today is higher than the average number per flight a year ago. 这个选项只说了n>m 但是等式中还有别的变量D和d不清楚 所以不能确定
(E) The criteria that Breezeway Airlines uses for permitting passengers to buy discount coach tickets on the Toronto-to-Dallas route are different today than they were a year ago. 无关
至此这道题才算完结 | 
