Bunuel wrote:
A car averages 55 mph for the first 4 hours of a trip and averages 70 mph for each additional hour. The average speed for the entire trip was 60 mph. How many hours long is the trip?
A. 6
B. 8
C. 11
D. 12
E. 14
We can let the time for the remainder of the trip = t, and thus:
average speed = (distance 1 + distance 2)/(time 1 + time 2)
60 = (55 x 4 + 70t)/(4 + t)
60(4 + t) = 220 + 70t
240 + 60t = 220 + 70t
20 = 10t
t = 2
Thus, the trip was 4 + 2 = 6 hours.
Answer: A
_________________
5-star rated online GMAT quant
self study course
See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews