Aptitude - Problems on Trains - Discussion

Discussion Forum : Problems on Trains - General Questions (Q.No. 7)
7.
Two trains of equal length are running on parallel lines in the same direction at 46 km/hr and 36 km/hr. The faster train passes the slower train in 36 seconds. The length of each train is:
50 m
72 m
80 m
82 m
Answer: Option
Explanation:

Let the length of each train be x metres.

Then, distance covered = 2x metres.

Relative speed = (46 - 36) km/hr

   = 10 x 5 m/sec
18

   = 25 m/sec
9

2x = 25
36 9

2x = 100

x = 50.

Discussion:
232 comments Page 8 of 24.

SHUBHaM SaKHaRE said:   7 years ago
Let the length of both trains be 'x'.
Distance covered by slower train = 36*(36*5/18),
Hence total distance covered by faster train= 2x+36*(36*5/18),
Hence we get;
46*5/18=(2x+36*(36*5/18))/36,
By solving this on calc we get;
X=50.

Mohammad yasir said:   7 years ago
If the first train crosses slower train by relative speed 10kmph. It means the whole length of this train crosses slower train in 36 seconds.

Which literally means the same train crosses the slower train twice when we treat it a point.

Joydeep Mondal said:   7 years ago
From where 18/5 came?

Umer said:   7 years ago
How is the speed of the train mentioned as the length we needed?

Sridharsan said:   8 years ago
The first train covered a distance of 460m in 36s and the second one covered 360 m in 36s, at the moments of 36th second the distance between trains is 100 mtr, above said the answer is 50mtr, that is the fastest train is 50mtr away from the other one. That is, the train also passes before reaching 36s. If the question is true the answer would 100 mtr. Am I right?

Abhishek said:   8 years ago
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.

Faraz said:   8 years ago
Isn't it a case of relative speed. If it is can't we solve this problem by that method? please tell me.

Rabiul said:   8 years ago
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.

Priya biradar said:   8 years ago
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.

Vineetha said:   8 years ago
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.


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