Problem 6 · Total distance ÷ total time · 4 points
Made by AI and not reviewed by a real person.
Ala walks to school at 4 km/h and returns home by the same route at 6 km/h. What is her average speed for the whole round trip?
- 5.2 km/h
- 5 km/h
- 4.8 km/h
- 4.4 km/h
- 4.6 km/h
Show a hint
- Pick a convenient distance, say 12 km each way, and compute the total time.
Show the answer and solution
Answer: C — 4.8 km/h
Take 12 km each way: going takes 3 h, returning 2 h. Total: 24 km in 5 h → 4.8 km/h. The "obvious" 5 is wrong because Ala spends MORE TIME at the slower speed. Averages must be weighted by what actually accumulates (time) — a deep idea that reappears in statistics and physics.