Multiple choice

A motor-cycle covers 40 km with a speed of 20 km/hr. find the speed of the motor-cycle for the next 40 km journey so that the average speed of the whole journey will be 30 km/hr.

  1. 70 km/hr

  2. 52.5 km/hr

  3. 60 km/hr

  4. 60.5 km/hr
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Average speed = Total distance / Total time. Total distance = 80 km. Average speed = 30 km/hr. Total time = 80 / 30 = 8/3 hours. Time for first 40 km = 40 / 20 = 2 hours. Time for next 40 km = 8/3 - 2 = 2/3 hours. Speed for next 40 km = 40 / (2/3) = 60 km/hr.

AI explanation

The total distance is 40 km + 40 km = 80 km, and for an average speed of 30 km/hr, the total time required is 80 km / 30 km/hr = 8/3 hours. The time taken for the first 40 km is 40 km / 20 km/hr = 2 hours. The time remaining for the next 40 km is 8/3 hours - 2 hours = 2/3 hours, making the required speed 40 km / (2/3) hours = 60 km/hr.

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