a man is standing on a railway bridge which is 180 m long . he finds that a train crosses the bridge in 20 seconds but himself in 8 seconds . find the length of the train and its speed .
if length of train is l and speed of train is s , then l / s = 8 ( l + 180 ) / s = 20 ( l + 180 ) / l = 20 / 8 = 5 / 2 2 l + 360 = 5 * l 3 * l = 360 l = 120 mtrs s = l / 8 = 120 / 8 = 15 m / sec answer : b
speed(divide(divide(180, 20), subtract(inverse(8), inverse(20))), 8)