A train running at a speed of 54 km/hr crosses a platform of length same as that of the train in 36 seconds. If train B which is 230 meters long crosses the same platform in 25 seconds, then find the speed of train B (in km/hr).

Explanation

Let the length of the train be x. Then, the length of the platform is also x. Speed of train = 54 km/hr = 54 x (5/18) m/s = 15 m/s. According to the question: (x + x)/15 = 36 => 2x = 540 => x = 270 m. The length of the platform is 270 m. Now, a train of length 230 m crosses the platform in 25 sec. Let the speed of the train be v m/s. => (270 + 230)/v = 25 => v = 20 m/s. Speed of train = 20 m/s = 20 x (18/5) = 72 km/hr. Therefore, the speed of the train is 72 km/hr.