# A train 130 m long is moving at a speed of 120 km / h. It crosses a train 140 m long moving in the same direction along parallel tracks in 27 seconds.

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A train 130 m long is moving at a speed of 120 km / h. It crosses a train 140 m long moving in the same direction along parallel tracks in 27 seconds. What is the speed of the second train?
1. 66 km / h
2. 84 km / h
3. 102 km / h
4. 112 km / h

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Correct Answer - Option 2 : 84 km / h

Given:

Train length is 130m

The speed of the train is 120 km/h

Moving in the same direction of a train 140 m, and crosses in 27 seconds

Concept used:

When two objects move in the same direction speed is subtracted

When two objects move in the opposite direction speed is added.

Speed = Distance/Time

To convert speed km/h into m/s we multiply by 5/18 and vice versa

Calculation:

Total length is

⇒ 130 + 140 = 270 m

Let the speed of the other train be s km/h

Let Relative speed be r = 120 - s

⇒ r = 270/27 = 10 m/s

Convert speed into km/h multiply by 18/5

⇒ 10 × (18/5) = 36 km/h

Speed of the other train is

⇒ 36 = 120 - s

⇒ s = 120 - 36 = 84 km/h

∴ The speed of the other train is 84 km/h