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:
478 comments Page 5 of 48.
Suja said:
4 months ago
How it 18รท5 will become? Please explain.
(11)
Jeyadurga Ramkumar said:
12 months ago
@All
Here they mentioned the relative time of the train to the man is 10 seconds which means the train's length(i.e 125m) has just passed the moving man in 10 seconds,so we need to find the relative speed for the train to the man as mentioned below.
i.e, 125/10 =25/2 m/s as it is in m/s,we need to convert into km/hr
25/2 x 18/5 = 45 km/hr (relative speed between train and man)
Next we need to find the original speed of the train that passes the man's speed with the help of the relative speed between the train and man i.e,45 km/hr(,if the Direction of the man and train is opposite to one another, then do addition, if both man and train running in same direction subtract both )
Here man and train are in the same direction.
So subtract;
Let x be the speed of the train and we know the man's speed as 5 km/hr and the relative speed is 45 km/hr.
Since same direction subtraction,
x = 45+5
x = 50 km/hr (answer)
By checking:
Train's speed =50 km/hr ,,man's speed = 5 km/hr, same direction so do subtraction;
50 -5 = 45 to get the relative speed of both.
Here they mentioned the relative time of the train to the man is 10 seconds which means the train's length(i.e 125m) has just passed the moving man in 10 seconds,so we need to find the relative speed for the train to the man as mentioned below.
i.e, 125/10 =25/2 m/s as it is in m/s,we need to convert into km/hr
25/2 x 18/5 = 45 km/hr (relative speed between train and man)
Next we need to find the original speed of the train that passes the man's speed with the help of the relative speed between the train and man i.e,45 km/hr(,if the Direction of the man and train is opposite to one another, then do addition, if both man and train running in same direction subtract both )
Here man and train are in the same direction.
So subtract;
Let x be the speed of the train and we know the man's speed as 5 km/hr and the relative speed is 45 km/hr.
Since same direction subtraction,
x = 45+5
x = 50 km/hr (answer)
By checking:
Train's speed =50 km/hr ,,man's speed = 5 km/hr, same direction so do subtraction;
50 -5 = 45 to get the relative speed of both.
(10)
Apoorva Marathi said:
1 year ago
How it is 50? please explain to me.
(9)
Raghu k said:
4 years ago
It is simple guys.
If we observe hint, her there should be the relative speed because the train and are travelling in the same direction so we (train) -v (man) T =Distance.
(120/10) (18/5) =v (t) -5.
45+5=v (t).
50=v (t).
If we observe hint, her there should be the relative speed because the train and are travelling in the same direction so we (train) -v (man) T =Distance.
(120/10) (18/5) =v (t) -5.
45+5=v (t).
50=v (t).
(8)
Sanika prakash said:
3 months ago
Good answer. Thanks all for explaining the answer.
(8)
Priyanka devi said:
4 years ago
@Rahul.
Great work, Thanks for explaining.
Great work, Thanks for explaining.
(7)
Preetilata Das said:
5 months ago
Someone, please explain this question properly.
(7)
Moses Obia said:
4 years ago
Where was 18 got from? Please explain.
(6)
Bunny said:
4 years ago
Why the speed of the train is calculated by 125 meters by 10sec?
(6)
Jothi said:
2 decades ago
Please explain to sutract -5 but ans is 50.
(4)
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