A vehicle goes a certain distance at 60 km/h and returns the same distance at 40 km/h. What is the average speed for the round trip?

Problem Statement

For equal distances, average speed is the harmonic mean. Two a b over a plus b. Two times sixty times forty over one hundred gives forty eight.

SolutionRead Only

Vavg = 2ab/(a+b) = 2×60×40/(60+40) = 48

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