Understanding the argument -
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. - Background info. Example:
The price of the tickets last year was $200, and say the inflation is 5%. If we were to take inflation into account, this year's price would be $210. But as the price remains the same, this year will still be $200.
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. - "However" introduces the contrast. Example:
Last year - Full price = $200
50% at a discounted price, say for $100
50% at Full price
Average = 50% * 100 + 50% *200 = $150
This year = Full price = $200
90% at a discounted price say for $100
10% at Full price
Average = 90% * 100 + 10% *200 = $110
Therefore, on average, people pay less today in constant dollars for a Breezeway Toronto-to-Dallas coach ticket than they did a year ago. - Conclusion
Which one of the following, if assumed, would allow the conclusion above to be properly drawn?
Option Elimination - We need to find an assumption, missing premise, or assumption.
(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. - "level of service" is out of scope.
(B) A Toronto-to-Dallas discount coach ticket on Breezeway Airlines costs about the same in constant dollars as they did a year ago. - Yes. The discounted prices of $100 are the same as last year and this year. Say if this is not true. If the discount price this year is $190, then the average price will be = 90% * 190 + 10% * 200 = $198. Then the conclusion breaks as the price from last year has increased from $150 to $198.
(C) All full-fare coach tickets on Breezeway Airlines cost the same in constant dollars as they did a year ago. - Restating the premise. Wrong.
(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. - " The average number of coach passengers per flight" is out of scope from an "on average, people pay less today" perspective.
(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. - Yes, it may be, but that doesn't help with the scope, which is to find the missing premise for the conclusion: "On average, people pay less today in constant dollars for a Breezeway Toronto-to-Dallas coach ticket than they did a year ago."