swerve wrote:A car traveled 60 mph from Belnap to Lincoln and 50 mph from Lincoln to Belnap. If the whole trip was 660 miles, how long did the round trip take?
A. 6 hours
B. 11 hours
C. 12.1 hours
D. 13.2 hours
E. 24.2 hours
The OA is C.
Please, can any expert explain this PS question for me? I'm not sure why that is the correct answer. Thanks.
Here's a quick solution.
Let's see what happens if the car travels at the SAME SPEED for the entire 660 miles.
Time = distance/speed
IF the car traveled 60 mph for the entire 660 miles, then...
Travel time = 660/60 = 11 hours
Since the car traveled at a SLOWER speed of 50 mph for half of the trip, we can conclude that
the entire trip took longer than 11 hours to complete
ELIMINATE A and B
IF the car traveled 50 mph for the entire 660 miles, then...
Travel time = 660/50 = 66/5 = 13.2 hours
ASIDE: Here's a brief video explaining a very fast way to quickly divide ANY number by 5 in your head: https://www.gmatprepnow.com/module/gene ... video/1112
Since the car traveled at a FASTER speed of 60 mph for half of the trip, we can conclude that
the entire trip took less than 13.2 hours to complete
ELIMINATE D and E
By the process of elimination, the correct answer must be C
Cheers,
Brent
