Aptitude - Problems on Trains - Discussion

46-36 = 10,
10*5/18 = 2.77,
2.77*36s = 100,
So, the length of train is 100/2 = 50m.

The relative speed = (46-36)=10km/h.
converted into m/s = 10 * 5/18 = 25/9m/s -------------------------- 46km/h train 1 faster train
(x) 36 sec -------------------------- 36km/h train 2 slower train.
Find out the length of the train (distance) d = s * t.
25/9 * 36 = 100both train.
100/2 find the each train distance,
50.

The simple math is, 46km/1h - 36km/1h= 10km/1h. Now; it can be converted into meter/second that is 10km*1000m/3600sec. 10000m/3600s= 2.778m/1sec.


Now, for the difference of 2.778 meter/1sec the faster train cross the slower train in 36 sec. So, the distance the faster train cross 36sec * 2.778 meter= 100 meters.
This 100 meters distance/way is the length of two trains (faster&slower).
As if, two trains' length is same. So, one train's length is; 100/2= 50 meters.

Why the distance are substrated?

I mean 460-360. Please explain in detail.

@Sarita.

As per relative motion law. If two particle moves in the same direction then you have to subtract their speed and if in opposite direction the add it.

Same direction of trains.
So, (46-36)km/hr = 10km/hr.
Conversion, 10*5/18 =25/9 m/s.
To find length of two trains,
Length=speed*time.
25/9 * 36 =100.

Since 2 trains, 100/2=50.

FASTER Train travels in 36 SECOND
(46 X 5 /18) X 36 = 460 M.

SLOWER Train travels in 36 SECOND
(36 X 5/18) X 36= 360 M.

Therefore 460-360= 100 M (length if both train) as both train travels 36 sec. And as both the trains are equal than the length of each train will be (100/2)= 50 m.

At the point of overtaking by train B in 36 seconds.

The Speed of 1st train = 46km/hr,
Convert it into m/s===== 46*5/18=115\9,
length= speed*time
=115/9*36=460m
Speed of 2nd train = 36km/hr --> convert it into ms=====36*5/18=10
length= speed*time
= 10*36=360m
= 460-360=100

For 2 train 100/2=50m.

Since t1 has covered the other train distance and after crossing the train2 it must be having length same x metres from the starting point of train2. In order to calculate length, we have taken 2x metres.

Isn't it a case of relative speed. If it is can't we solve this problem by that method? please tell me.