arithmetic - a train 125 m long passes a man running at 5 kmph in the same direction in which the train is going in 10 seconds the speed of the train is - skillgun

Speed of the train relative to man = [125/10] m/sec = [25/2] m/sec.
= [25/2 * 18/5] km/hr = 45 km/hr.
Let the speed of the train be x kmph. Then, relative speed = (x - 5) kmph.
? x - 5 = 45 or x = 50 kmph.