BTGmoderatorLU wrote:Source: GMAT Prep
Jane walked for 4 miles. What was her average speed for the first 2 miles?
1) Jane's average speed for the 4 miles was 3.2 miles per hour.
2) It took Jane 15 minutes longer to walk the second 2 miles than it took her to walk the first 2 miles.
The OA is C
Let's take each statement one by one.
1) Jane's average speed for the 4 miles was 3.2 miles per hour.
No information about the first 2 miles and the second 2 miles. Insufficient.
2) It took Jane 15 minutes longer to walk the second 2 miles than it took her to walk the first 2 miles.
Say time taken by Jane for the first 2 miles is x hours; thus, the time taken by her for the second 2 miles = x + 15/60 = (x + 0.25) hours
Thus, average speed = 4/(x + x + 0.25)
Since we do not know the average speed, we can't get the answer. Insufficient.
(1) and (2) together
average speed = 4/(x + x + 0.25) = 3.2
=> x = 0.5 hours
Jane's average speed for the first 2 miles = 2/0.5 = 4 mph. Sufficient.
The correct answer:
C
Hope this helps!
-Jay
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