Identify the Question Stem: The question indicates that the information given supports one of the following conclusions—that is, the conclusion can be found in the answer choices. This is an Inference question.
Deconstruct the Argument: From 2000 to 2004, average fuel efficiency was 25 miles per gallon, while from 1995 to 1999, it was only 20 miles per gallon. From 2000 to 2004, the average price was $2 per gallon, but from 1995 to 1999, it cost only $1.60 per gallon.
Pause and State the Goal: On Inference questions, the argument will provide a series of facts and the correct answer will be something that can be definitively proven from at least some of those facts. On Inference questions, trap answers will often conclude something that might be true but that cannot be definitively proven from the facts given in the argument.
Work from Wrong to Right:
(A) Beware of predictions on Inference questions. Unless the argument specifically says so, you can't assume that a particular trend will continue. This could happen but it can't be definitively proven from the information given.
(B) This one is tricky! The cost of gasoline was higher in the later period, not the earlier period. Was the length of an average trip the same in both periods? The argument doesn't say. It could be the case that, on average, people took shorter trips in either the earlier or the later period.
(C) It's probably true that some people do shop for more fuel-efficient cars when fuel prices increase, but this can't be definitively proven by the information given in the argument.
(D) CORRECT. This is complicated; write it out. The ratio efficiency : price was 20 : $1.60 in the earlier period and 25 : $2 in the later period. Normally when you're simplifying ratios, you try to get the numbers down to the smallest integers, but when one of your values is in dollars (or any other currency), don't hold yourself to the requirement that you have to have integers. Simplify the other set of values, 20 and 25, as far as you can:
Earlier period ratio = 20 : $1.60. Divide both sides by 4 to get 5 : $0.40.
Later period ratio = 25 : $2. Divide both sides by 5 to get 5 : $0.40.
The ratios for the two periods do indeed simplify down to the same ratio, so this statement can be proven to be true.
(E) They did spend more money per gallon on gasoline, but the argument doesn't provide any info to calculate how much gas people bought overall. They may have bought less gas in the later period and so could have spent less money on gas overall during that period.
The correct answer is (D).
