Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 9)
9.
Two trains are moving in opposite directions @ 60 km/hr and 90 km/hr. Their lengths are 1.10 km and 0.9 km respectively. The time taken by the slower train to cross the faster train in seconds is:
Answer: Option
Explanation:
Relative speed = (60+ 90) km/hr
| = |  |
150 x | 5 |  m/sec |
| 18 |
| = | |
125 | m/sec. |
| 3 |
Distance covered = (1.10 + 0.9) km = 2 km = 2000 m.
| Required time = | |
2000 x | 3 | sec = 48 sec. |
| 125 |
Discussion:
107 comments Page 3 of 11.
Sumit said:
1 decade ago
Length of the two trains=2km (the units I have taken is all in kms).
Relative speed is 150km/hr (this too in kms).
S=Length/Time=>time=length/speed.
Time=2/150=1/75 of a second i.e., 1/75*60 (converted into minutes) =4/5.
4/5*60 (into seconds) =48 sec.
Relative speed is 150km/hr (this too in kms).
S=Length/Time=>time=length/speed.
Time=2/150=1/75 of a second i.e., 1/75*60 (converted into minutes) =4/5.
4/5*60 (into seconds) =48 sec.
Nil said:
1 decade ago
Here is the simple way.
60+90 km/hr = 150 km/hr = 150*1000/3600 = 41.66 m/sec (trains relative speed in mtr/sec)
Distance covered = 1.10+0.9 km = 2 km = 2000 m
Time taken by slower/faster train is the same = 2000/41.66 (time = distance/speed)= 48
60+90 km/hr = 150 km/hr = 150*1000/3600 = 41.66 m/sec (trains relative speed in mtr/sec)
Distance covered = 1.10+0.9 km = 2 km = 2000 m
Time taken by slower/faster train is the same = 2000/41.66 (time = distance/speed)= 48
Ankit said:
1 decade ago
Hi All,
How can be the time taken by the faster train to cross the slower train is same?
The faster train is about 30 Kmph faster than the slower train..
Since the speeds are relative, I think time factor should also be relative.
Please suggest
How can be the time taken by the faster train to cross the slower train is same?
The faster train is about 30 Kmph faster than the slower train..
Since the speeds are relative, I think time factor should also be relative.
Please suggest
Avinash Upadhyay said:
1 decade ago
@Divyan, here we are converting the speed into meter/sec from km/hr .
(1km = 1000m
1hr = 3600sec
m/sec = 1000/3600 = 5/18.)
150*25/3 = 125/3.
And relative speed comes into picture when two given objects in the questions are in motion.
(1km = 1000m
1hr = 3600sec
m/sec = 1000/3600 = 5/18.)
150*25/3 = 125/3.
And relative speed comes into picture when two given objects in the questions are in motion.
Pankaj said:
7 years ago
Hi, the time taken by faster train to cross slower & time taken by slower train to cross faster will be same, right?
So why are we using relative speed formula for all the time. We can use a+b/u+v for calculating time.
So why are we using relative speed formula for all the time. We can use a+b/u+v for calculating time.
Vijju said:
8 years ago
Here we need to consider the only length of faster trains because the question asked for the time taken by slower to pass fast train. So that what I think we need to consider relative speed but faster train length.
Sekhar said:
1 decade ago
Hi, I have a doubt
60+90= 150KM/hr i,e speed
distance covered is 1.10+0.9=2.0 km
Then you want time T=D/S = 2/150=1/75 in km/hr
You want to change in Mts 1/75*5/18 here iam not getting 48 sec.
60+90= 150KM/hr i,e speed
distance covered is 1.10+0.9=2.0 km
Then you want time T=D/S = 2/150=1/75 in km/hr
You want to change in Mts 1/75*5/18 here iam not getting 48 sec.
ParthShah said:
1 decade ago
Point 1: Trains are running in opposite directions so the slower train will cross the faster one.
Point 2: The time taken by slower train to cross faster train would be equal to the vice versa.
Point 2: The time taken by slower train to cross faster train would be equal to the vice versa.
Shalinwilson said:
7 years ago
No need to convert to m/s.
Because everything in m and h.
Simply relative speed = 60+90 = 150 km/h.
Distance = 1.1+9 = 2 km.
2/150 = .013 hr (in seconds its .013*60 *60 = 48 seconds.
Because everything in m and h.
Simply relative speed = 60+90 = 150 km/h.
Distance = 1.1+9 = 2 km.
2/150 = .013 hr (in seconds its .013*60 *60 = 48 seconds.
(2)
Riyaz said:
1 decade ago
Hi friends. I have one doubt when the trains are moving in opposite direction we add the speed of those trains but why we have to add the length of the two trains. Please explain me.
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