a train traveling at 108 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 ?
"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 = 108 kmph * 12 seconds convert 108 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 ) . ∴ 108 kmph = 5 / 18 ∗ 108 = 30 m / sec therefore , length of the platform = 30 m / s * 12 sec = 360 meters . choice b"
subtract(multiply(divide(multiply(108, const_1000), const_3600), 30), multiply(divide(multiply(108, const_1000), const_3600), 12))