Question

a car travels 100km at a speed of 60kmperh and returns with a speed of 40kmperh .calulate the averge speed

Answer 1

Average speed= 2xy/(x+y)
                        = 2×40×60/40=60
Let the distance at one side be= x
so the total distance= 2x

Time taken to travel the journey= x/60
Time taken to return back from the journey= x/40
  
so, total time= x/60 + x/40= 100x/2400

Average speed= Total distance/ total time= 2x/(100x/2400)
                                                                  = 48km/h

Hope that helps you!!