alleryA car travels 60 km at 30 km/h and returns 60 km at 60 km/h. What is the average speed for the round trip?
A$45$ km/h
B$48$ km/h
C$40$ km/h
D$50$ km/h
Answer & Solution
Correct answer: C. $40$ km/h
**Equal-distance harmonic mean:** 2×30×60/(30+60) = 3600/90 = 40 km/h.
(Arithmetic mean 45 is the trap.)
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