Multiple choice

A boy running at 10/9th of his actual speed covers 39 km in 2 hours 20 minutes and 24 seconds. Find the actual speed of the boy (approx.).

  1. 15 km/hr

  2. 37 km/hr

  3. 23 km/hr

  4. 150 km/hr

  5. N/A
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A Correct answer
Explanation

Time = 2 hours 20 minutes 24 seconds = 2 + 20/60 + 24/3600 = 2 + 1/3 + 1/150 = (300 + 50 + 1)/150 = 351/150 hours. Speed = Distance / Time = 39 / (351/150) = 39 * 150 / 351 = 150 / 9 = 16.66 km/hr. Since this is 10/9 of actual speed, actual speed = 16.66 * 9/10 = 15 km/hr.

AI explanation

First, convert the given time of 2 hours 20 minutes and 24 seconds entirely into hours, which is 2 + (2040/3600) hours, equaling 117/50 hours. The speed corresponding to this time is 39 divided by (117/50), resulting in 50/3 km/hr. Since this speed is 10/9 of his actual speed, we multiply by the reciprocal fraction: (50/3) multiplied by (9/10). The actual speed of the boy is 15 km/hr.

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