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:
481 comments Page 4 of 49.
Vinoda patil said:
2 years ago
To convert m/s to km/hr we use direct formula,
i.e 18/5.
Here,1km/hr = 5/18 m/sec.
To convert a given data from m/sec to km/hr we use 18/5.
i.e 18/5.
Here,1km/hr = 5/18 m/sec.
To convert a given data from m/sec to km/hr we use 18/5.
(27)
Shanthi said:
2 years ago
How this 18/5 come? please explain to me.
(17)
Sayak Chakraborty said:
2 years ago
How 18/5 came after 25/2? Please answer.
(16)
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)
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)
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)
Preethiammu said:
2 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.
(264)
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)
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