Multiple choice

A bus travelled the first one-third distance at a speed of 10 kmph, the next one-third at 20 kmph and the remaining distance at 60 kmph. Find the average speed of the bus.

  1. 18 kmph

  2. 16 kmph

  3. 9 kmph

  4. 48 kmph
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A Correct answer
Explanation

Average speed = Total distance / Total time. Let total distance be 3D. Time = (D/10) + (D/20) + (D/60) = (6D + 3D + 1D) / 60 = 10D/60 = D/6. Average speed = 3D / (D/6) = 18 kmph.

AI explanation

Assuming the total distance is 60 km, each one-third segment is 20 km, meaning the bus takes 2 hours for the first part, 1 hour for the second part, and 20 divided by 60 hours for the final part. The total time taken is 2 plus 1 plus 0.33, which equals 3.33 hours or 10 divided by 3 hours. The average speed equals total distance divided by total time, calculated as 60 divided by (10/3), yielding 18 kmph.

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