1.  A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:
A. 45 km/hr
B. 50 km/hr
C. 54 km/hr
D. 55 km/hr

Answer: Option B

Explanation:

Speed of the train relative to man = 125 m/sec
10

   = 25 m/sec.
2

   = 25 x 18 km/hr
2 5

   = 45 km/hr.

Let the speed of the train be x km/hr. Then, relative speed = (x - 5) km/hr.

x - 5 = 45         x = 50 km/hr.