Hi All,

When dealing with "rounding" questions, you have to make sure that you're properly following the 'rules' of rounding.

Cindy's distance is rounded to the nearest 10 miles and is "called" 290 miles. This means that the actual distance is given by the following inequality:

285 <= Actual distance < 295

In that same way, that number of gallons used is rounded to the nearest gallon and is "called" 12 gallons. This means that the actual number of gallons used is given by the following inequality:

11.5 <= gallons used < 12.5

The question asks for the "range" that the actual MILES/GALLON falls into. This is ultimately a question of "ratios" and what it takes to make a ratio as "big" as possible or as "small" as possible.

To make a ratio "bigger", you can EITHER make the numerator bigger OR make the denominator smaller. To get the "biggest" ratio, you have to do BOTH. In that same way, to make a ratio "smaller", you can EITHER make the numerator smaller OR make the denominator bigger. To get the "smallest" ratio, you have to do BOTH.

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

richewalsh wrote:I got the question, right but one aspect is bothering me and I'm sure it is just an oversight or rookie mistake, but any help is much appreciated.

On a recent trip, Cindy drove her car 290 miles , rounded to the nearest 10 miles, and used 12 gallons of gasoline, rounded to the nearest gallon. The actual number of miles per gallon that Cindy's car got on this trip must have been between?

a - 290/12.5 and 290/11.5

b - 295/12 and 285/11.5

c - 285/12 and 295/12

d - 285/12.5 and 295/11.5

e - 295/12.5 and 285/11.5

If the distance of 290 miles is obtained by rounding to the nearest 10 miles, the actual distance must be between 285 miles and 295 miles. Similarly, if the number of gallons of gasoline used, 12 gallons, is obtained by rounding to the nearest gallon, the actual number of gallons must be between 11.5 gallons and 12.5 gallons. Therefore, the maximum number of miles per gallon is 295/11.5 and the minimum number of miles per gallon is 285/12.5, and the actually number of miles per gallon is some number in between these two numbers.

Note that we maximized the number of miles per gallon by making the numerator as large as possible (295) and the denominator as small as possible (11.5). Similarly, to minimize the mpg, we made the numerator as small as possible (285) and the denominator as large as possible (12.5).

Answer: D