Question

A train 280 metres long is running at a speed of 42 km/hr.how much time will it take to pass a man standing on a platform?

Answer 1

time=distance/speed 

42*5/18m/s
280*18/42*5=24sec

Answer 2

The length of the train is 280m.
Therefore to cross the man it has to cover a distance of 280m.
Speed of the train = 42km/h=42000m/h.
time = distance/speed
Therefore time taken to cross the man is= 280/42000 h
                                                                     = 280/42000*3600sec
                                                                         =24 sec
                                                          
                                                                       
                                                                     
                                                      hope it helps  : )