34.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?
A.120m B.20m
C.25m D.None
Sol. Let the length of the train be x metres,
Then, the train covers x metres in 8 seconds and (x + 180) metres in 20 sec
x/8=(x+180)/20 รณ 20x = 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
