Engineering Board Exam Reviewer · Physics · hard
A car travels from A to B at 40 km/h and returns from B to A at 60 km/h along the same road. What is its average speed for the round trip?
- 50 km/h
- 100 km/h
- 48 km/h
- 20 km/h
Answer
C. 48 km/h
Solution
Average speed = total distance/total time = 2d/(d/40 + d/60) = 2(40)(60)/(40 + 60) = 48 km/h (harmonic mean).
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