Question

A car travels 100 km at a speed of 60 kilometre per hour and returns with a speed of 40 kilometre per hour calculate the average speed for the whole Journey

Answer 1

Time taken to go = 100/60=5/3hr
time taken to return = 100/40=5/2hr
total distance = (100+100)km = 200km
total time taken = (5/3 + 5/2)hr = 25/6 hr 
average speed = total distance / total time 
                            =200/25/6
                            =200*6/25
                            =48kmph
hence average speed is 48 kmph



hope it helps%

Answer 2

1st Case ( going )

Speed = 60km/h
Distance = 100km
Time = Distance/speed
= 100/ 60 hours

2nd case ( returning )


Speed = 40km/h
Distance = 100km
Time = distance/time
= 100/40 hours


Total Distance = 100+100= 200 km
Total time = 100/40 + 100/60
= 25/6 hours


Now,

Average Speed = total distance / total time
= 200/(25/6)
= 48km/h



Answer is 48km/h





- Abhinav Singh