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 15 of 24.

Semanth said:   1 decade ago
If faster train passes the slower train in 36 seconds then slower train passes the faster train in how many seconds?

Tintu said:   1 decade ago
Cant we do like:
relatv speed=10km/hr
Time=36 sec=.6hr
Then 2x distance is given by 10*.6 hours=6hrs
So x=3hrs

D. R. Chaudhary said:   1 decade ago
Two trains are on parallel lanes then the one has to cross only 100 m or say x. So the correct answer is 100.

Siree said:   6 years ago
s1-s2=(L1+L2)/time.
46-36=2(L1+L2)/36,
10 * 5/18=2(L1+L2)/36,
50=2(L1+L2)/2,
50*2=2(L+1L2).
L1+L2=100/2 = 50.

Mahesan said:   1 decade ago
The 2nd train has 36 sec, 1st train speed has 2 times of the slower train, so it is calculated as above ?

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.

Nelson said:   6 years ago
Why have you subtracted the speeds to get the relative speeds instead of adding them? Please explain.

Suntth said:   1 decade ago
How the relative velocity is V2-V1? Since tthe trains are in same direction, velocity shall be V1+V2

Pankaj said:   7 years ago
Why are we calculating relative speed?

I used 36= 2x/(46+36). Using this getting 410m. Am I right?

Prati said:   1 decade ago
I think we can do like:

Relative speed is (46-36);

Length = (10*5/18)*36;
=100both
=50 each.


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