Abdul, while driving to school, computes the average speed for his trip to be 20 km/h. On his return trip along the same route, there is less traffic and the average speed is 30 km/h. What is the average speed of Abdul's trip? 

Asked by reshma.sami13 | 28th Sep, 2021, 07:52: PM

Expert Answer:

Let distance between home and school be d km
 
Time taken from home to school = distance / time = ( d / 20 ) hr.
 
Time taken from school to home = distance / time = ( d / 30 ) hr.
 
Total travel time = ( d/20 ) + ( d/30 ) =  (5d/60)  hr =  (d /12) hr
 
average speed = Total distance / time = (2d) / (d/12) = 24 km/hr

Answered by Thiyagarajan K | 28th Sep, 2021, 09:57: PM