CR: Gas Mileage

[akash.kank]

The following question is from the CR guide, 5th edition:

The average fuel efficiency of vehicles sold nationwide during the period 2000- 2004 was 25 miles per gallon; the corresponding figure during the period 1995- 1999 was 20 miles per gallon. The national average price of gasoline during the period 2000-2004 was $2 per gallon; the corresponding figure during the period 1995-1999 was $1.60 per gallon.

The statements above, if true, best support which of the following conclusions?

A)The average fuel efficiency of vehicles sold nationwide should reach 30 miles per gallon for the period 2005-2009.

B)The national average price of gasoline during 1997 was lower than the cor­ responding price during 2003.

C) Rising gasoline prices led consumers to purchase more fuel-efficient cars.

D)Between the two described time periods, the national average fuel effi­ciency and the national average gasoline price both increased at roughly the same rate.

E)Consumers spent more money on gasoline during the period 2000-2004 than during the period 1995-1999.

The OA given is D due to the 25% rise. However, the statement seems to suggest that both, fuel efficiency and national average gasoline price, increased at the same rate, NOT "by" the same "percentage".

For example, maybe the fuel efficiency increased to 25 on the first day of 2000 and stayed there till 2004, giving the average of 25. The gasoline price, on the other hand, may have increased gradually and infact may even have been on the higher side of the average for some amount of time.
In this case, doesn't the statement that they both increased at the same rate seem wrong?
By elimination, I would go for C.

Thanks!

[Jazmet]

Not sure about the explanation that you seek. But in the conclusion type questions, I would never go beyond what passage states. The passage doesn't even talk about fuel-efficient cars, hence I'd think 10 times before choosing option 'C'.

Also, the option D does mention the phrase the national average in both the cases "fuel efficiency and gasoline price' hence it clearly talks about the averages moving up at the same rate.

1999 - miles per gasoline - 12.5
2005 - miles per gasoline - 12.5

Instructors - Please correct me if I am wrong.

[jnelson0612]

Jazmet is 100% right that on Draw a Conclusion questions you should NEVER go beyond what the passage would support. After every answer choice you need to ask yourself "does this HAVE to be true based on the facts in the passage?" If it doesn't HAVE to be true it's not the answer.

Now, let's talk about why D is correct.

D)Between the two described time periods, the national average fuel effi­ciency and the national average gasoline price both increased at roughly the same rate.

Did they increase at the same rate?
Average fuel efficiency was 20 and rose to 25. change/original amount is 5/20, equivalent to a 25% increase
Average gas price was $1.60 and rose to $2. 25% increase

So D is indeed true . . . the national average fuel efficiency and the national average gas price increased at roughly the same rate (actually, exactly at the same rate).

[Jazmet]

Thanks JN! :)

[jnelson0612]

Thanks JN! :)

My pleasure! That was a very good point that too few students know/understand. Good for you!