Two trains travel in opposite directions at 36 km/hr and 45 km/hr respectively. A man sitting in the slower train passes the faster train in 8 s. What will be the length of the faster train?

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80 m

120 m

150 m

180 m

answer is D.

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Detailed Solution

Concept: In this question, we need to find the length of the train using the concept of relative velocity and relation of speed, distance and time.
Relative velocity of a body wrt. another body id the velocity of the body by bringing the reference body in rest.
Given: Velocity of fast train:

Velocity of the slow train:

Relative velocity of the fast train wrt. the slow train:

Now, converting 81 km/hr into m/s

We know that,

So, length of train =

Hence, option (4) is correct; the length of the faster train is 180 m.

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