Quantitative Aptitude 2 - (problems on Train.)

This chapter deals with the speed , time  and the distance covered by a moving train . There are mainly two types of questions that will come in the exams.

1. Train passing a static object .
2. Train passing a moving object (Or more likely another moving train) .

Before starting the chapter we should know a very little but most important convertion :-

(1) X km/hr = {X * (5/18)} m/s    (2) X m/s = {X * (18/5)} km/s

So without wasting anymore time let's get started ........

1.  Train passing a static object :-

             When a train passes a static object then the total distance covered by the train is.....           

 Length covered by the train = The length of the train + The length of the object
             

           [If the length of the object is very small say for the length of a light post 

              then the length is considered as zero .]

Therefor the formula for this portion will be .........

          (Length Covered by the train) / speed = Time required to pass the object.

  Q) A train 100 m long is running at the speed of 30kmph. Find the time taken by it to pass a man standing near railway station.

 Q) A train is moving at a speed of 132 kmph . If the length of the train is 100 meters, how long it will take it to cross a railway station platform 165 meters long ?

    2.  Train passing another moving object (or another train):-

               When a train passes a static object then the total distance covered by the train is.....           

 Length covered by the train = The length of the first train + The length of the second train 

    [Let the speed of First Train is "S1" and the speed of Second Train is "S2"]

Now in these types of problem there can occur two types of situations .

a) Case 1 :- 

Two trains are moving in the same direction. For this case the formula will be :-

   (Length Covered by the train) / (S1 - S2) = Time required to pass the object.

Q) Two trains 100 meters and 120 meters long are running in the same direction with speed 72kmph and 54kmph . In how much time will the first train cross the second ?  

b) Case 2 :- 

Two trains are moving in the opposite direction. For this case the formula will be :-

   (Length Covered by the train) / (S1 + S2) = Time required to pass the object.

Q) Two trains 137 mt and 163 mt in length are running towards each other on parallel lines , one at the rate of 42 kmph and another at 48 kmph . In what time will they be clear each other from the moment they meet ? 

So these are the main two types . But there is another type which is not that important but there is no harm in learning right ? 

Ok so that type suggests ......

When two trains start from point A & B and after crossing each other they reach to the point B & A respectively then......

           

                 (A's speed ) : (B's speed ) = (√b : √a ) 

Q) Two trains one from Hyderabad to Delhi and other from Delhi to Hyderabad start simultaneously. After they meet the trains reach their destinations after 9 hours and 16 hours respectively . What is the ratio of the speed ?  

So this is it from this chapter hope the logic is clear now . If you have any kind of  doubt , suggestion , query then let me know in the comment section .Keep sharing the knowledge and keep learning :) .