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 33 of 48.
Roopa said:
1 decade ago
Hi friends,
Here length of train = speed*time.
Likewise speed of train = length/time.
-> 125/10 = (25/2)m/sec.
Now given 5km/hr.
So speed is (x-5)km/hr or (x-5)(5/18).
Here we goes -> (25/2)m/sec = (x-5)(5/18).
-> (25/2)*(18/5) = (x-5).
-> 45 = (x-5).
-> x = 45+5.
-> x = 50 km/hr.
Here length of train = speed*time.
Likewise speed of train = length/time.
-> 125/10 = (25/2)m/sec.
Now given 5km/hr.
So speed is (x-5)km/hr or (x-5)(5/18).
Here we goes -> (25/2)m/sec = (x-5)(5/18).
-> (25/2)*(18/5) = (x-5).
-> 45 = (x-5).
-> x = 45+5.
-> x = 50 km/hr.
Aditya said:
1 decade ago
The train and man are moving in the same direction so. If we want to take out the speed of any one of them, then we have to take one object as stationery.
Iyyanar said:
1 decade ago
Please give a clear cut definition for relative velocity.
Arjun said:
1 decade ago
Speed of man*time = 5*10 = 50.
Navaneedhar said:
1 decade ago
Please explain the subtract value of (x-5)?
Veena said:
1 decade ago
Why train speed has to be subtracted with man speed?
Akansha said:
1 decade ago
18/5 is used to change meter per second to kilometer per hour.
And I have no idea why it says -5 as it should be +5.
And I have no idea why it says -5 as it should be +5.
Gayu said:
1 decade ago
Why its divided by 15/8? need some brief explanation.
Praveen said:
1 decade ago
Friends its a simple logic that if a men travel along the same direction of the train then the train speed is subtracted if it travel in opposite direction then train speed is added.
Hope you understand take this logic in your mind and solve any problem.
Hope you understand take this logic in your mind and solve any problem.
Nirmal K Sahoo said:
1 decade ago
Man speed 5 km/hr, So man's speed per second (5*5/18) m/s.
After 10 sec, train passes the man, so, man cover distance in 10 sec is :
5*5*10/18 = 13.89m.
So, train covered total distance in 10 sec is :
125 m+13.89 m = 138.89 m.
So, speed of train is :138.89/10 m/s = 13.889*3600/1000 Km/hr = 50 Km/hr.
After 10 sec, train passes the man, so, man cover distance in 10 sec is :
5*5*10/18 = 13.89m.
So, train covered total distance in 10 sec is :
125 m+13.89 m = 138.89 m.
So, speed of train is :138.89/10 m/s = 13.889*3600/1000 Km/hr = 50 Km/hr.
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