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:
233 comments Page 6 of 24.
Siree said:
7 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.
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.
Dhruvi said:
7 years ago
Is the faster train behind the slower one? Is that why we are adding length of both?
Nelson said:
7 years ago
Why have you subtracted the speeds to get the relative speeds instead of adding them? Please explain.
Hemant manglani said:
7 years ago
Same Direction (46-36) = 10,
length= speed * time.
(10*5/18)*36 = 50.
length= speed * time.
(10*5/18)*36 = 50.
Debojit said:
7 years ago
But they are in the same direction, How you add x+ x and not subtract?
Because it's given the same direction if it's opposite direction then it's not a problem. Please explain me.
Because it's given the same direction if it's opposite direction then it's not a problem. Please explain me.
Sumit Bhagat said:
7 years ago
If length of each train is supposed as x. Then how could distance cover is 2x?
Myuri said:
7 years ago
@Tejaswini.
Our question is to find the length of each train. So first we want to find both the length of the trains (2x), here x is a length of one train. So only take 2x.
Our question is to find the length of each train. So first we want to find both the length of the trains (2x), here x is a length of one train. So only take 2x.
Tejaswini said:
7 years ago
How did you take 2x?
Sunil said:
7 years ago
Since they are in same speed u,v.
We take u-v=46-36=10km/hr,
10*5/18=25/9,
So now we know the speed and time,
25/9 * 36 = 100.
As we calculated for the 2 trains we require only the length of one train so we take 100/2=50.
We take u-v=46-36=10km/hr,
10*5/18=25/9,
So now we know the speed and time,
25/9 * 36 = 100.
As we calculated for the 2 trains we require only the length of one train so we take 100/2=50.
UMAR farooq said:
7 years ago
First, it has to pass its complete length then it crosses the slowest train means;
First it takes 18 sec to travel its own length then it takes another 18 sec to cross the slowest train that's why 2x it is taken.
First it takes 18 sec to travel its own length then it takes another 18 sec to cross the slowest train that's why 2x it is taken.
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