Multiple choice

A car travels one-third of the distance on a straight road with a velocity of 10 km/hr, the next one-third with a velocity of 20 km/hr and the last one-third with a velocity of 60 km/hr. What is the average velocity of the car for the whole journey?

  1. 10 km/hr

  2. 18 km/hr

  3. 29 km/hr

  4. 33 km/hr
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Average velocity = Total distance / Total time. Let distance be 3d. Time = d/10 + d/20 + d/60 = (6d+3d+d)/60 = 10d/60 = d/6. Average velocity = 3d / (d/6) = 18 km/hr.

AI explanation

For a journey where equal distances are covered at different speeds, the average velocity equals the harmonic mean of those speeds. If we assume the total distance is 60 km, each one-third portion is 20 km, and the times taken for the three portions are 2 hours, 1 hour, and 1/3 of an hour respectively. The total time is 10/3 hours, so the average velocity is 60 km divided by 10/3 hours, resulting in 18 km/hr.

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