Question

Abdul, while driving to school, computes the average speed for his trip to be 20 kmh-1 . On his return trip along the same route, there is less traffic and the average speed is 30 kmh-1 . What is the average speed of Abdul’s trip?

August 25, 2024

Answer

Let one side distance = x km.

Time taken for forward trip at a speed of 20 km/h = Distance / Speed = x/20 h.

Time taken in return trip at a speed of 30 km/h = x/30 h.

Total time for the whole trip = ${{x \over20} + {x \over30} = {{3x + 2x} \over60} = {5x \over60}}$ h.

Total distance covered = 2x km.

We know, Average speed = Total distance ÷ Total time

= 2x ÷ (5x/60) = 24 kmh^-1 .

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