Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 2)
2.
A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:
Answer: Option
Explanation:
| Speed of the train relative to man = |  |
125 |  m/sec |
| 10 |
| = | |
25 | m/sec. |
| 2 |
| = | |
25 | x | 18 | km/hr |
| 2 | 5 |
= 45 km/hr.
Let the speed of the train be x km/hr. Then, relative speed = (x - 5) km/hr.
x - 5 = 45 
x = 50 km/hr.
Discussion:
487 comments Page 5 of 49.
Keerthana P Tawade said:
3 years ago
T = L/V1-V2
Where
T = time taken by train to pass the pole
L = Length of the train.
V1 = velocity of the train.
V2= Velocity of the man.
10 = 125/V1-5kmph.
v1-5kmph = 125/10*18/5 (converting m/s into km/h).
V1-5kmph = 45kmph,
V1 = 50kmph.
Where
T = time taken by train to pass the pole
L = Length of the train.
V1 = velocity of the train.
V2= Velocity of the man.
10 = 125/V1-5kmph.
v1-5kmph = 125/10*18/5 (converting m/s into km/h).
V1-5kmph = 45kmph,
V1 = 50kmph.
(108)
Shani sharma said:
3 years ago
If we consider man as stationary then the velocity of train is;
Vt=125/10
=12.5 m/s.
Here, the velocity of man is given which is Vm= 5 km/hr.
We have to convert the velocity of the train m/s into km/s.
Then we get,
Vt= 12.5 × 3600/1000 km/hr.
= 45km/hr.
Now, the velocity of the train wrt man.
Vtm= Vt +Vm.
= 45 +5.
= 50 km/hr.
Vt=125/10
=12.5 m/s.
Here, the velocity of man is given which is Vm= 5 km/hr.
We have to convert the velocity of the train m/s into km/s.
Then we get,
Vt= 12.5 × 3600/1000 km/hr.
= 45km/hr.
Now, the velocity of the train wrt man.
Vtm= Vt +Vm.
= 45 +5.
= 50 km/hr.
(91)
Preethiammu said:
3 years ago
Very nice, thanks everyone for explaining the answer.
(28)
Berman said:
3 years ago
Distance covered in crossing.
When the train crosses a stationary object or pole or another train.
The distance covered by the train = length of the train.
So, the length of the train is 125 m =distance covered by the train.
and we know that it took 10 sec to pass the man.
Train Speed = speed of man*time taken by the train to pass,
Speed = 5km/hr * 10sec.
Speed = 50km/hr.
When the train crosses a stationary object or pole or another train.
The distance covered by the train = length of the train.
So, the length of the train is 125 m =distance covered by the train.
and we know that it took 10 sec to pass the man.
Train Speed = speed of man*time taken by the train to pass,
Speed = 5km/hr * 10sec.
Speed = 50km/hr.
(265)
Sheital saira said:
3 years ago
@Hemanth sairam.
Why 60 mins and 60 seconds taken there?
Please explain me.
Why 60 mins and 60 seconds taken there?
Please explain me.
(19)
Atharv S Shelar said:
3 years ago
@All.
All asking the same doubt "why it is 18/5 and not 5/18"?
It is because the conversion for m/s to km/hr is 18/5 and for km/hr to m/s is 5/18.
All asking the same doubt "why it is 18/5 and not 5/18"?
It is because the conversion for m/s to km/hr is 18/5 and for km/hr to m/s is 5/18.
(53)
Hemanth Sairam said:
3 years ago
Let's think man is standing like a pole
125mtrs/10 secs = 12.5 mtrs per sec,
Convert seconds to hours;
12.5 mtrs x 60mins x 60 seconds = 45000 mtrs per hr,
= 45kmph.
The man also moving with some speed right, so the train will take some extra speed to cross than the man
So 45+5 = 50kmph actual train speed.
125mtrs/10 secs = 12.5 mtrs per sec,
Convert seconds to hours;
12.5 mtrs x 60mins x 60 seconds = 45000 mtrs per hr,
= 45kmph.
The man also moving with some speed right, so the train will take some extra speed to cross than the man
So 45+5 = 50kmph actual train speed.
(96)
Sourabh said:
3 years ago
Given data :
Length Of the Train 125 meters.
Speed of Man = 5 km/hr
Speed of train = ?
Time = 10 sec.
Distance = Time * Velocity (speed).
125 = 10 × v,
V = 125/10,
V = 25/2 M/sec Now Convert it into Km/hr,
V = 25/2 × 18/5,
V = 45 km/hr.
And given In The Question train And Man Is Traveling in Same Direction.
V = Speed of train - Speed Of Man.
45 = Speed of train - 5.
Speed of train = 45+5.
Speed of train = 50 km/hr.
Length Of the Train 125 meters.
Speed of Man = 5 km/hr
Speed of train = ?
Time = 10 sec.
Distance = Time * Velocity (speed).
125 = 10 × v,
V = 125/10,
V = 25/2 M/sec Now Convert it into Km/hr,
V = 25/2 × 18/5,
V = 45 km/hr.
And given In The Question train And Man Is Traveling in Same Direction.
V = Speed of train - Speed Of Man.
45 = Speed of train - 5.
Speed of train = 45+5.
Speed of train = 50 km/hr.
(181)
Owona Julius said:
3 years ago
How - 5 came? Please explain this step.
(17)
Chinnupradhan said:
3 years ago
S = L/T.
S = 125/10
S = 25/2.
then,
M/sec to km/hr convert.
1km/hr = [1000m/3600sec] = 5/18m/sec,
m/sec = 18/5km/hr.
i.e
(25/2 * 18/5)km/hr,
45km/hr.
Therefore first train x-5 = 45.
X = 50 km/hr.
S = 125/10
S = 25/2.
then,
M/sec to km/hr convert.
1km/hr = [1000m/3600sec] = 5/18m/sec,
m/sec = 18/5km/hr.
i.e
(25/2 * 18/5)km/hr,
45km/hr.
Therefore first train x-5 = 45.
X = 50 km/hr.
(30)
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