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A train running at uniform speed passes a bridge 300 m long in 15 sec and another bridge 450 m long in 21 sec. Find:- (i) The length of the train (ii)The speed of the train in km/h

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by reishumwi

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by reishumwi

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Length of the train = L meters.

Distance travelled by the train to cross the bridge is the length of the bridge plus length of the train.

Speed of the train = distance / time interval

= (300 + L) m / 15 sec = (450 + L) / 21 sec

=> 21 (300 + L) = 15 (450 + L)

=> 2100 + 7 L = 2250 + 5 L

=> 2 L = 150

=> L = 75 meters.

Speed of the train = (300 + 75) meters / 15 sec = 25 m/sec

= 25 * 18/5 = 90 km/hour

Distance travelled by the train to cross the bridge is the length of the bridge plus length of the train.

Speed of the train = distance / time interval

= (300 + L) m / 15 sec = (450 + L) / 21 sec

=> 21 (300 + L) = 15 (450 + L)

=> 2100 + 7 L = 2250 + 5 L

=> 2 L = 150

=> L = 75 meters.

Speed of the train = (300 + 75) meters / 15 sec = 25 m/sec

= 25 * 18/5 = 90 km/hour