Answer : 2. "420 m"
Explanation :

Answer: B) 420 m Explanation: Let the length of the stationary train Y be LY Given that length of train X, LX = 300 m Let the speed of Train X be V. Since the train X crosses train Y and a pole in 60 seconds and 25 seconds respectively. => 300/V = 25 ---> ( 1 ) (300 + LY) / V = 60 ---> ( 2 ) From (1) V = 300/25 = 12 m/sec. From (2) (300 + LY)/12 = 60 => 300 + LY = 60 (12) = 720 => LY = 720 - 300 = 420 m Length of the stationary train = 420 m