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A man covered a certain distance in 3 parts with average speeds of 20 km/h, 30 km/h, and 60 km/h. What is his average speed over the entire journey, assuming equal distances?

1. 30 km/h
2. 35 km/h
3. 40 km/h
4. 45 km/h

Correct answer: 30 km/h

Solution

When equal distances are covered at different speeds, average speed = total distance / total time. For equal distances, this becomes the harmonic mean of the speeds. Here, average speed = 3 / (1/20 + 1/30 + 1/60) = 30 km/h.

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