Question

On a 120 km track a train travel the first 30 km at a uniform speed of 30 km/h . Calculate the speed with which train should move rest of the track so as the average 60 km /h for the entire trip

Answer 1

                           ANSWER                            

                          In the first 30 km speed of the train, v1 = 30 km/h

                          Speed of the train in the next 90 km, v2 (to be determined)

                         Average speed = 60 km/h = (v1 + v2)/2  

                                         = (30 km/h + v2)/2  

                              → v2 = 90 km/h