Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND EditionHow long did it take Betty to drive nonstop on a trip from her home to Denver, Colorado?
(1) If Betty's average speed for the trip had been 3/2 times as fast, the trip would have taken 2 hours.
(2) Betty's average speed for the trip was 50 miles per hour.
Target question: What was Betty's travel time?This is a great candidate for
rephrasing the target questionLet D = The distance driven
Let R = Betty's average speed
Since Time = Distance/Rate, we can rephrase the target question. . .
REPHRASED target question: What is the value of D/R?Statement 1: If Betty's avg speed for the trip had been 1.5 times as fast, the trip would have taken 2 hours. The distance is still the same (D), but the rate is 1.5R
So, statement 1 tells us that D/1.5R = 2
Is this enough information to find the value of
D/R?
Sure, just take the equation D/1.5R = 2 and multiply both sides by 1.5 to get
D/R = 3Since we're able to answer the
REPHRASED target question with certainty, statement 1 is SUFFICIENT
Statement 2: Betty's avg speed for the trip was 50 miles per hour.This tells us that R=50
However, we cannot find the value of
D/R, since we don't know the value of D (distance)
So, statement 2 is NOT SUFFICIENT
Answer: A
RELATED VIDEO FROM OUR COURSE