51. A train 50 m long passes over a bridge at a velocity of 30 km/hr. If it takes 36 s to cross the bridge, then the length of the bridge will be:
(a) 100 m (b) 200 m (c) 250 m (d) 300 m
Speed = 30 km/h = 30 * 5/18 m/sec = 50/6 m /sec
Distance of covered by train = Speed x time = 36 * 50/6 = 300 m
The length of the bridge = (Distance covered by train-l of the train)=300-50 = 250 m