7)
The distance between Athens and Carthage is 120 miles. A car travels from Athens to Carthage at 60 miles per hour and returns from Carthage to Athens along the same route at 40 miles per hour. What is the average speed for the round trip?
(A) 48
(B) 50
(C) 52
(D) 56
(E) 58
Answer: Choice A is correct. Average speed = Total distance / Total time. A car traveling at 40 mph will cover 120 miles in 3 hours. A car traveling at 60 mph covers the same 120 miles in 2 hours. The total travel time is therefore 5 hours.
For the entire round trip, the average speed = (120 + 120) / 5 = 48 mph.