A car drives 120 km at 60 km/h and then another 120 km at 40 km/h. What is its average speed for the whole trip?
Answer and explanation
Correct answer: B. km/h
- Step 1: The times are hours and hours, so the trip takes 5 hours. Step 2. The average speed is total distance over total time: km/h. **Answer: km/h. Why not the others:** is the plain mean of the two speeds, which ignores that more time is spent at the slower speed, and and are further slips.
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