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:
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 6 of 24.
Puja said:
1 decade ago
Why we need to subtract 46-36 and what is relative speed?
RKS NITJ said:
1 decade ago
This is the simplest example of relative speed.
Ammu said:
1 decade ago
Hai how this 36 came? I didn't get it can you please explain clearly? why 2x? why 36 not 46?
Ram said:
1 decade ago
I think answer is 100 because if we calculate x as 100m then the.
Another train length will be same because both are equal.
Another train length will be same because both are equal.
The Guide said:
1 decade ago
In the above problem it is given that the lengths of two trains are equal.
according to theory if both trains are moving in same directions then the lenghts will be subtracted but this is the case that both lenghts are different but in the above problem the lenghts are equal in this case we have to add lengths without regarding their directions so lenght is 2x
but as the trains are moving in same directions their relative speeds must be subtracted
so (46-36)*5/18
2x/(50/18)=36
2x=36*(50/18)
x=50m
according to theory if both trains are moving in same directions then the lenghts will be subtracted but this is the case that both lenghts are different but in the above problem the lenghts are equal in this case we have to add lengths without regarding their directions so lenght is 2x
but as the trains are moving in same directions their relative speeds must be subtracted
so (46-36)*5/18
2x/(50/18)=36
2x=36*(50/18)
x=50m
Anonymous said:
1 decade ago
How can we conclude that distance covered is 2x because here both the trains are moving and hence along with covering the distance 2x, they will cover some more distance. Please make this thing clear.
Sonali said:
1 decade ago
I can't get,please tell me, Why did we get 46-36? why didn't we get (46+36)
and why did we get 2x/36?
Please explain me.
and why did we get 2x/36?
Please explain me.
Sarvepalli.rajasekhar said:
1 decade ago
Since the Trains are moving in the same direction The diff between their speeds has to be calculated.
46 kmph - 36 kmph = 10 kmph
convert into meters per second 10 x 1000 meters / 3600 seconds
We get 25/9.
Now apply formula distance = speed x time = 25/9 x 36
Cancelling 36 with 9 we get 4 multiply with 25 we get 100 meters, which is the length of two trains.
As per the question the two trains length is the same there fore each train length is 50 meters.
46 kmph - 36 kmph = 10 kmph
convert into meters per second 10 x 1000 meters / 3600 seconds
We get 25/9.
Now apply formula distance = speed x time = 25/9 x 36
Cancelling 36 with 9 we get 4 multiply with 25 we get 100 meters, which is the length of two trains.
As per the question the two trains length is the same there fore each train length is 50 meters.
Shro said:
1 decade ago
For all those who got doubt why 46-36?
Its because both train are moving in same direction.
So as per the formula when moving in same direction.it should be subtracted.
When moving in opposite direction,it should be added.
Its because both train are moving in same direction.
So as per the formula when moving in same direction.it should be subtracted.
When moving in opposite direction,it should be added.
Shro said:
1 decade ago
We are supposed to find length of each train .
But both train are moving in same direction.
So let the length of each train be x respectively.
So the distace covered will be x+x=2x metres
But both train are moving in same direction.
So let the length of each train be x respectively.
So the distace covered will be x+x=2x metres
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers