Time, Speed & Distance
Aptitude

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Q.

A man sitting in train travelling at the rate of 50 km/hr observes that it takes 9 sec for a goods train travelling in the opposite direction to pass him. If the goods train is 187.5m long. Find its speed

 A.

40 km/hr

 B.

30 km/hr

 C.

24 km/hr

 D.

25 km/hr

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Solution:
Option(D) is correct

Let the speed of goods train be $x$ km/hr.

Then,

\((50+x)\times \dfrac{5}{18}=\dfrac{187.5}{9}\)

⇒ x= 25 km/hr

Edit: For more insights into the solution check comment by Ketaki.


(2) Comment(s)


Namrata Dash
 ()

Why the length of the train is not taken into consideration here?


Ketaki
 ()

Whenever we deal with such questions where there is a passenger sitting in a train and another train passes by, we dont add the length of that train to calculate the total distance in the formula i.e. Time = (length of train 1 + length of train 2)/ Relative Speed. In this case we would only take the length of 1 train (187.5m in this case) and time (9 sec) to derive at speed 25 km/hr.