A train 100 m long passes a man, running at 15 km/hr in the same direction in which the train is going, in 20 seconds. The speed of the train is:  Options:
A) 16 km/hr.
B) 33 km/hr.
C) 21 km/hr.
D) 49 km/hr.
E) 76 km/hr.
Speed of the train relative to man =100/20m/sec=5 m/sec.   =5 x	18/5	km/hr   = 18 km/hr.   Let the speed of the train be x km/hr. Then, relative speed = (x - 15) km/hr.   x - 15 = 18   x = 33 km/hr.   ANSWER:33 km/hr.
<result>B</result>
A train 100 m long passes a man, running at 15 km/hr in the same direction in which the train is going, in 20 seconds. The speed of the train is: