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A train passes a pole in 20 seconds and a bridge in 60 seconds. What is the length of the bridge, if the length of the bridge is 50 m more than the length of the train?

A train passes a pole in 20 seconds and a bridge in 60 seconds. What is the length of the bridge, if the length of the bridge is 50 m more than the length of the train? Correct Answer 100 m

Given:

Train passes to a pole in 20 second

Concept:

Speed = Distance/Time

Calculation:

Let us assume the length of the train is X m and the length of the bridge is (X + 50) m

Since, Train passes a pole in 20 sec 

So, Speed of train = Length of train/ Time to cross the pole 

⇒ Speed of train = X/20

Now, Train crosses a bridge in 60 sec 

So, Speed of train = (Length of train + Length of bridge)/Time to cross the bridge

⇒ Speed of train = (X + X + 50)/60 = (2X + 50)/60

⇒ X/20 = (2X + 50)/60

⇒ X = (2X + 50)/3

⇒ 3X = 2X + 50

⇒ X = 50

∴ The length of the bridge is 100 m.

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