A train traveling at 144 kmph crosses a platform in 30 seconds and a man standing on the platform in 12 seconds. What is the length of the platform in meters? Choices:
A) 240 meters
B) 360 meters
C) 480 meters
D) 600 meters
E) Cannot be determined
Answer   Distance covered by the train when crossing a man and when crossing a platform   When a train crosses a man standing on a platform, the distance covered by the train is equal to the length of the train.   However, when the same train crosses a platform, the distance covered by the train is equal to the length of the train plus the length of the platform.   The extra time that the train takes when crossing the platform is on account of the extra distance that it has to cover. i.e., length of the platform.   Compute length of platform   Length of the platform = speed of train * extra time taken to cross the platform.   Length of platform = 144 kmph * 12 seconds   Convert 144 kmph into m/sec   1 kmph = 5/18 m/s (This can be easily derived. But if you can remember this conversion, it saves a good 30 seconds).   ∴ 144 kmph = 5/18∗144 = 40 m/sec   Therefore, length of the platform = 40 m/s * 12 sec = 480 meters.   480 metershoice 480 meters
<result>C</result>
A train traveling at 144 kmph crosses a platform in 30 seconds and a man standing on the platform in 12 seconds. What is the length of the platform in meters?