Multiple choice

The average speed of a car in a race that covers three trial laps at the speed of 200, 200 and 250 km/hr, respectively is

  1. 214.28 km/hr

  2. 211.36 km/hr

  3. 218.66 km/hr

  4. 225 km/hr

  5. 216.67 km/hr
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A Correct answer
Explanation

Average speed for equal distances is the harmonic mean of the speeds. Harmonic mean of 200, 200, 250 = 3 / (1/200 + 1/200 + 1/250) = 3 / (0.005 + 0.005 + 0.004) = 3 / 0.014 = 214.2857.

AI explanation

Assuming each trial lap covers an equal distance, we calculate the average speed using the harmonic mean formula for three speeds: average speed equals 3 divided by the sum of the reciprocals of the speeds. This gives 3 divided by (1 divided by 200 plus 1 divided by 200 plus 1 divided by 250), which simplifies to 3 divided by 0.014. The average speed for the three laps is 214.28 km/hr.

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