As part of his journey, a person travels 120 km at 80 km/h, the next 100 km at 40 km/h, and comes back to the starting point at 75 km/h. The average speed of the person throughout the journey (approximately) is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e 63.46 km/h.
Average speed = total distance/total time
Time = distance/speed
Time taken to travel 120 km = 120/80 = 3/2 = 1.5 hr
Time taken to travel 100 km = 100/40 = 5/2 = 2.5 hr
Time taken to travel 220 km = 220/75 = 2.93 hr
Average speed = (120 + 100 + 220)/(1.5 + 2.5 + 2.93) = 440/6.93 = 63.46 km/hr