aman88 wrote:When a car traveled from Town A to Town B without stopping, the car traveled a total of 2m miles, where m > 0. The car traveled the first m miles at an average speed of v miles per hour, and the car traveled the entire 2m miles at an average speed of 5v/3 miles per hour. What was the average speed of the car, in miles per hour, when it traveled the final m miles?
A. 8v/3
B. 4v
C. 5v
D. 16v/3
E. 8v
Let m=15 and v=3.
Time for the first m miles = d/r = m/v = 15/3 = 5 hours.
Time for the entire 2m miles = d/r = (2m)/(5v/3) = (2*15/( 5*3 / 3 ) = 6 hours.
Since the time for the entire 2m miles is 6 hours, and the time for the first m miles is 5 hours, the time for the last m miles = 6-5 = 1 hour.
Average speed for the last m miles = d/t = 15/1 = 15 miles per hour. This is our target.
Now we plug v=3 into the answers to see which yields our target of 15.
Only
C works:
5v = 5*3 = 15.
The correct answer is
C.
Last edited by
GMATGuruNY on Mon Dec 31, 2012 9:37 am, edited 1 time in total.
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