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:
476 comments Page 45 of 48.
Hemanth Sairam said:
2 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)
Atharv S Shelar said:
2 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)
Sheital saira said:
2 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)
Berman said:
2 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.
(262)
Preethiammu said:
2 years ago
Very nice, thanks everyone for explaining the answer.
(28)
Shani sharma said:
2 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)
Keerthana P Tawade said:
2 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)
Sunil said:
2 years ago
First, let's convert man running speed into second.
5000 ÷ 3600 = 1.38888.
3600 second is equal to 1hr.
1.38888 × 10 second
Why we multiply because we want to know how much the man covered meters in 10 seconds.
So the man covered in 10sec..
Is that 13.88888 then let's multiply.
13.8888×3600 = 50,000 meter
(3,600 is second)
Convert meter into km.
50,000÷1000= 50km.
The answer is 50km train speed.
5000 ÷ 3600 = 1.38888.
3600 second is equal to 1hr.
1.38888 × 10 second
Why we multiply because we want to know how much the man covered meters in 10 seconds.
So the man covered in 10sec..
Is that 13.88888 then let's multiply.
13.8888×3600 = 50,000 meter
(3,600 is second)
Convert meter into km.
50,000÷1000= 50km.
The answer is 50km train speed.
(61)
Sayak Chakraborty said:
2 years ago
How 18/5 came after 25/2? Please answer.
(16)
Shanthi said:
2 years ago
How this 18/5 come? please explain to me.
(17)
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