A train travelling at 48 kmph completely crosses another train having half its length and travelling in opposite direction at 42 kmph, in 12 seconds. It also passes a railway platform in 45 seconds. The length of the platform is
Choose the correct choice from the following: A) 400 m B) 450 m C) 560 m D) 600 m E) 680 m

Rationale: length of the ist train = 2 x m and the length of the other train be x m ( 1 / 2 ) the relative speed of the train ( 48 + 42 ) = 90 kmph or 25 m / s time taken to cross one another = 12 s hence , 12 = 2 x + x / 25 solving , x = 100 m and 200 m now to determine the length of the platform 45 = 100 + length of the platform / speed of the ist train 45 = 100 + l / 240 / 18 ( 48 kmph = 240 / 118 m / s ) solving , we get l = 600 m answer : d
Answer: D