# Question Video: Finding the Time Needed by a Train Moving with Uniform Velocity to Pass Another Train

A train A of length 90 m was travelling at a speed of 170 km/h. It passed by another train of length 205 m. Find the time required for train A to completely pass train B, given that train B is moving with a speed of 152 km/h in the same direction as train A.

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### Video Transcript

A train of length 90 meters was travelling at a speed of 170 kilometers per hour. It passed by another train of length 205 meters. Find the time required for train A to completely pass train B, given that train B is moving with a speed of 152 kilometers per hour in the same direction as train A.

In order to solve this problem, we need to know two facts. Firstly, one meter per second is equal to 3.6 kilometers per hour. This is because there are 1000 meters in a kilometer and there are 3600 seconds in an hour. Secondly, we’ll need to use the formula that time is equal to distance divided by speed as we need to calculate the time required for train A to completely pass train B.

The difference in speed between the two trains is 18 kilometers per hour. This means that train A is moving 18 kilometers per hour faster than train B as 170 minus 152 is equal to 18. Using our conversion that one meter per second is equal to 3.6 kilometers per hour, we can divide 18 by 3.6, which gives us a difference in speed of five meters per second.

The total length of the trains was 295 meters as train A was 90 meters and train B was 205 meters 90 plus 205 is 295. Therefore, in order to calculate the time required for train A to completely pass train B, we can divide the distance 295 by the speed five. This is equal to 59 seconds. Therefore, it requires 59 seconds for train A to completely pass train B.