2016 · Q38
A train is travelling at 48 km/hour completely crosses another train having half its length and travelling in opposite direction at 42 km/hour in 12 s. It also passes a railway platform in 45 s. What is the length of the platform ?
Elementary MathematicsTime, Speed and Distance
- A600 m
- B400 m
- C300 m
- D200 m
Explanation
Relative speed = 48+42 = 90 km/h = 25 m/s; in 12 s the trains cover 300 m = L+L/2, so the first train's length L = 200 m. Passing the platform: (200+P)/(48×5/18) = 45 s gives 200+P = 600, so the platform is 400 m long (option B).