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 13 of 24.
Akanksha said:
10 years ago
Relative speed, u-v = 10 = 10*(5/18) = 25/9 m/s.
We know that, t = a+b/u-v.
And time of crossing the slower train is given, i.e. = 36.
Also length of both is same so a = b,
So, 2a/(25/9) = 36, which results a = 50 and as b is equal to a, hence b = 50 as well.
We know that, t = a+b/u-v.
And time of crossing the slower train is given, i.e. = 36.
Also length of both is same so a = b,
So, 2a/(25/9) = 36, which results a = 50 and as b is equal to a, hence b = 50 as well.
Raghav said:
1 decade ago
In question given that both trains are running in same direction.
So in generalize form we assume that both the trains are started from same point.
So distance covered should be equal to x.
And x=100. I think 100 is the right answer.
So in generalize form we assume that both the trains are started from same point.
So distance covered should be equal to x.
And x=100. I think 100 is the right answer.
Javid Mir said:
1 decade ago
We know for same direction, relative speed = (V1-V2).
Now, V1 = 46 Km/hr & V2 = 36 m/hr or we can say;
V1 = 46x5/18 m/s & V2 = 36x5/18 m/s.
Now, Relative Speed = Length or Distance/Time,
i.e (46x5/18) - (36x5/18) = length/36.
Take 5/18 common we get,
5/18(46-36) = length/36.
Length = 5/18x10x36, on solving we get, length = 100 meters.
But since length of trains is same.
Hence length of each train will be, length = 100/2 => length = 50 meters.
Now, V1 = 46 Km/hr & V2 = 36 m/hr or we can say;
V1 = 46x5/18 m/s & V2 = 36x5/18 m/s.
Now, Relative Speed = Length or Distance/Time,
i.e (46x5/18) - (36x5/18) = length/36.
Take 5/18 common we get,
5/18(46-36) = length/36.
Length = 5/18x10x36, on solving we get, length = 100 meters.
But since length of trains is same.
Hence length of each train will be, length = 100/2 => length = 50 meters.
Ram said:
1 decade ago
There first train is crossing the next train so when it crosses the fast train train will cross it's length and and second train length. So there relative speed and their combined lengths are taken.
Kiran said:
1 decade ago
Speed = distance/time.
Here they have given that two trains are running parallel i.e., S1 & S2.
Relative speed = S1-S2 => 46-36 = 10kmph.
Now we have to convert kmph into m/sec.
So 10x5/18 = 25/9.
Speed = 25/9.
Time = 36 secs.
=>distance = speed x time.
=>25/9x36.
=>100 (length of the two trains).
Length of the each train = 50.
Here they have given that two trains are running parallel i.e., S1 & S2.
Relative speed = S1-S2 => 46-36 = 10kmph.
Now we have to convert kmph into m/sec.
So 10x5/18 = 25/9.
Speed = 25/9.
Time = 36 secs.
=>distance = speed x time.
=>25/9x36.
=>100 (length of the two trains).
Length of the each train = 50.
Edwin said:
1 decade ago
@Sandy.
I was confused too but I figured it out.
They use km/hr in the first place, and want to convert km/hr to m/sec.
Which is 100(m)/360(sec) (As we know that meter is 100 and sec is 60x60 in hour).
Therefore it will be 5/18 m/sec.
Hope you get it.
I was confused too but I figured it out.
They use km/hr in the first place, and want to convert km/hr to m/sec.
Which is 100(m)/360(sec) (As we know that meter is 100 and sec is 60x60 in hour).
Therefore it will be 5/18 m/sec.
Hope you get it.
Sandy said:
1 decade ago
How did you get 5/18?
Joydeep mukherjee said:
1 decade ago
There are two train A and B:
Let, the length of train A = X meter.
And, the length of train B also = X meter.
Then, the total length = (A+B) = (X+X) = 2X meter.
Relative speed = (46-36) km/hr = 10km/hr.
[Because, one train is faster then other].
Then, convert into m/sec = 10*5/18 = 25/9 m/sec.
As we know, Speed = Length/Time.
25/9 = 2X/36.
X = 50 [ by solving].
Let, the length of train A = X meter.
And, the length of train B also = X meter.
Then, the total length = (A+B) = (X+X) = 2X meter.
Relative speed = (46-36) km/hr = 10km/hr.
[Because, one train is faster then other].
Then, convert into m/sec = 10*5/18 = 25/9 m/sec.
As we know, Speed = Length/Time.
25/9 = 2X/36.
X = 50 [ by solving].
Sagor Chandro said:
1 decade ago
Why length of two train is needed? Please explain. The first train has to cross the length of single train only. Some body explain please.
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.
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