A car travels from city A to city B at an average speed of 60 km/h and returns at an average speed of 40 km/h. What is the average speed for the round trip?
Correct: A
To find the average speed for the round trip, we first need to find the total distance and the total time. However, since the distance each way is not given, let's denote the distance from A to B as D. Then, the total distance for the round trip is 2D. The time taken to travel from A to B at 60 km/h is D/60, and the time to return at 40 km/h is D/40. The total time is D/60 + D/40, which simplifies to (2D + 3D)/120 = 5D/120 = D/24. The average speed is total distance / total time, which is 2D / (D/24) = 48 km/h.