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 15 of 24.
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.
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.
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.
Ghanshyam said:
1 decade ago
There is some data is not given properly that the faster train start from ending point of slower train that's why the answer is 100 meters and if the trains start from same point at that time answer is 100 meters.
Akanksha said:
1 decade 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.
Vichu119 said:
10 years ago
Ya if t trains are running from same starting point above answer is wrong because length of train is 100 meter. If the faster train's front starts from slower train's back then the length of train is 50 mt.
Bharathi said:
10 years ago
I can't understand can anyone explain clearly?
Why we take 2x inspite 2 trains are equal length but they reach different distance only then how it possible?
Why we take 2x inspite 2 trains are equal length but they reach different distance only then how it possible?
SAM said:
10 years ago
Why should we take relative speed is (46-36) in this case they are parallel?
Patani said:
10 years ago
2x/36=25/9 why use 36?
Viswanath said:
10 years ago
As two trains are in parallel (same direction). So we can subtract the speeds of other trains. Relative speed is (25/9) m/sec.
NOTE: Time in contact of 2 trains at a time MEANS the time at which faster train engine meet the last part of slower train TO faster train last part meet the engine of slower train.
Both trains relative speed = Distance of 2 trains/(Time in contact of 2 trains at a time).
(25/9) m/sec = 2x/36.
NOTE: Time in contact of 2 trains at a time MEANS the time at which faster train engine meet the last part of slower train TO faster train last part meet the engine of slower train.
Both trains relative speed = Distance of 2 trains/(Time in contact of 2 trains at a time).
(25/9) m/sec = 2x/36.
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