A train 250 m long passes a man, running at 10 km/hr in the same direction in which the train is going, in 10 sec, the speed of the train is :
Speed of the train relative to man = (250/10) m/sec = 25 m/sec.
= (25 * 18/5) km/hr
= 90 km/hr
Let the speed of the train be x km/hr. then, relative speed
= (x - 10) km/hr.
.'. x - 10 = 90
or x = 80 km/hr.
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