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
"explanation : let the length of the train be x meters , then , the train covers x meters in 8 seconds and ( x + 180 ) meters in 20 sec x / 8 = ( x + 180 ) / 20 ⇔ 20 x = 8 ( x + 180 ) < = > x = 120 length of the train = 120 m . speed of the train = ( 120 / 8 ) m / sec = m / sec = ( 15 × 18 / 5 ) kmph = 54 km answer : option c"
speed(divide(divide(180, 20), subtract(inverse(8), inverse(20))), 8)