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 3 of 24.

Judah said:   4 years ago
The train should be 100mtr. The solution converts both speeds of the 2 trains to m/s and multiply each m/s by 36 and get the difference of the speed at 36 sec, and that the answer.

Hope it will helps.
(3)

Khushnood Ali said:   2 years ago
Speed = distance/time.
Speed = 2x/36 (2x assumed as distance covered by train and 36secs time is given).

The relative speed = 25/9 (calcuated in solution)

From both equation relative speed and speed should be same that's why;
2x/36 = 25/9.
(3)

SRIRAM said:   5 months ago
If both trains were travelling in the same direction then we need to subtract the values, am I right?

Anyone, please clarify to me
(3)

AMGOTH SRIVASU said:   4 months ago
@All

Speeds of {train1:46km/h},{train2:36km/h}
Across each other in time 36s,

Here the two are in parallel directions travelling where the relative speed of parallel is (train1-train2)/2.
so: length = (t1 - t2)/2 * time.
length= (46km-36km)/2 * 36,
= 10km * 18,
= 10 * (5/18)m*18,
Therefore the length = 50m.
(3)

Shri.. said:   3 years ago
@Bushra Ahmed.

2x=25/9*36 = 900/9 = 100.
(2)

Aditya said:   4 months ago
@SRIRAM.

We have to add both train lengths assume with your hand both hands cross each other now slow the process when your left hand and right hand meet the length of your left-hand and right-hand not subtract.
(2)

Yoo said:   2 months ago
The Length of the train be x.
(u-v) = 46 - 36 = 10km/hr = 25/9,
T = (a+b)/(u-v).
T is the time difference of 36 sec.
(u-v)relative speed train moves in the same direction.

By Substitute all values;
36 = (x+x)/(25/9),
36 * 25/9 = 2x,
x = 50.
(2)

Shyam said:   1 decade ago
How can we take 2X there?
(1)

Madhav said:   6 years ago
Since they are moving in same direction relative speed is;
46-36=10Km/h= 10*(5/18)= 2.77m/s.

Relative Speed is =2.77m/s.

Speed=Distance/Time.

Distance=Speed*time=2.77*36=99.9==100.

Here 2 train having equal length = D=L=l+l=2l.
2l=100
so l=50.
(1)

Mahesh Kariya said:   5 years ago
((46-36)X(5/18)) = (50/18) = (100/36).
2X = 100.
X = 50.
(1)


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