If the speed of the train be 80 kmph and it takes 18 seconds to cross a platform. Next it takes 5 seconds to cross a cyclist cycling at the rate of 8 km/hr. in the same direction. What is the length of the platform?
B
Correct answer
Explanation
Convert speed to m/s: 80 kmph = 80 × 5/18 = 22 2/9 m/s. Cyclist speed = 8 × 5/18 = 20/9 m/s. Relative speed (same direction) = 22 2/9 - 20/9 = 180/9 = 20 m/s. Length of train = 20 × 5 = 100 m. Distance covered crossing platform = 22 2/9 × 18 = 400 m. Platform length = 400 - 100 = 300 m. Option B is correct.