# 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:
45 km/hr
50 km/hr
54 km/hr
55 km/hr
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:
453 comments Page 1 of 46.

MAHA said:   2 months ago
How 18/5? Please explain to me.
(27)

Adesh Katiya said:   2 months ago
l = 125m,
u = 5km/hr,
v = ?
t = 10s.
u - v = 125/10 m/s,
u - v = 25/2 m/s,
u - v = 5*9 km/hr,
u - v = 45km/hr,
5km/hr - v = 45km/hr.
v = 50 km/hr.
Hence, option (B).
(12)

Vinoda patil said:   3 months 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.
(20)

Shanthi said:   3 months ago
How this 18/5 come? please explain to me.
(15)

Sayak Chakraborty said:   4 months ago
(15)

Sunil said:   5 months 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.
(40)

Keerthana P Tawade said:   8 months 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.
(101)

Shani sharma said:   8 months 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.
(83)

Preethiammu said:   8 months ago
Very nice, thanks everyone for explaining the answer.
(26)

Berman said:   10 months 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.
(232)