Multiple choice

A and B are two towns. Mr. Faruqui covers the distance from A to B on a cycle at 16 km/hr. However, he covers the distance from B to A on foot at 9 km/hr. His average speed during the whole journey is

  1. 12.5 km/hr

  2. 10.25 km/hr

  3. 11.52 km/hr

  4. 12.32 km/hr
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Average speed = Total Distance / Total Time. Let distance be d. Time 1 = d/16. Time 2 = d/9. Total time = d/16 + d/9 = 25d/144. Average speed = 2d / (25d/144) = 288/25 = 11.52 km/hr.

AI explanation

When equal distances are travelled at two different speeds, the average speed is given by the Harmonic Mean formula: 2xy/(x+y). Substituting the speeds of 16 km/hr and 9 km/hr, we get (2 * 16 * 9) / (16 + 9). The numerator becomes 288 and the denominator is 25, giving an average speed of 11.52 km/hr.

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