alleryA train runs 60 km at 30 km/h, then another 60 km at 60 km/h. What is its average speed for the whole trip?
A36 km/h
B45 km/h
C50 km/h
D40 km/h
Answer & Solution
Correct answer: D. 40 km/h
Total distance 120 km takes 2 h plus 1 h, so 120 km in 3 h gives 40 km/h, not the simple mean.
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