Question

A car travel 100 km at a speed of 60km /h and return with a speed of 40km/h calculate the average speed of for the whole journey.

Answer 1

distance to be covered in both cases = 100 km
1st case,
speed,u = 60 km/h
so, time taken to cover distance,T1= distance/speed
                                                    =100/60
2nd case,
speed,v = 40 km/h
time taken,T2= 100/40
total distance = distance covered in 1st case + distance covered in 2nd case
                      = 100 +100 = 200 km
total time taken =T1+T2
                         =100/60 + 100/40 = 500/120 = 25/6 h = 4.166... h
average speed = total distance covered/total time taken
                         =200/4.16
                         =48.07... km/h