Multiple choice

Ravi travelled a distance of 60 km at the speed of 15 km/hr, another 40 km at the speed of 10 km/hr and then finally travelled the last 50 km. If his average speed is 15 km/hr, then the speed during 50 km distance is

  1. 20 km/hr

  2. 8.33 km/hr

  3. 12.5 km/hr

  4. 25 km/hr

  5. 16.66 km/hr
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Total distance = 60 + 40 + 50 = 150 km. Total time = (60/15) + (40/10) + (50/v) = 4 + 4 + 50/v = 8 + 50/v. Average speed = Total distance / Total time = 150 / (8 + 50/v) = 15. Solving: 150 = 15(8 + 50/v) => 10 = 8 + 50/v => 2 = 50/v => v = 25.

AI explanation

Using the basic Time, Speed and Distance formula, the time for the first 60 km is 60 divided by 15, which is 4 hours, and the time for the next 40 km is 40 divided by 10, which is 4 hours. The total distance is 150 km, and with an average speed of 15 km/hr, the total time taken is 150 divided by 15, which equals 10 hours. This leaves 2 hours for the final 50 km stretch. The required speed is 50 divided by 2, which equals 25 km/hr.

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