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:
475 comments Page 9 of 48.
ABHISHEK said:
6 years ago
The speed of train with respect to ground=125/10=25/2 (m/sec).
Now to covert into km/hr:(25/2)*(3600/1000)=45 Km/hr.
Now there is a formula:
Velocity of train w.r.t. man(45 km/hr)=velocity of train w.r.t. ground(let it be x) - velocity of man w.r.t. ground(5km/hr).
So,
45 = x-5.
i.e. x = 50 Km/hr.
Now to covert into km/hr:(25/2)*(3600/1000)=45 Km/hr.
Now there is a formula:
Velocity of train w.r.t. man(45 km/hr)=velocity of train w.r.t. ground(let it be x) - velocity of man w.r.t. ground(5km/hr).
So,
45 = x-5.
i.e. x = 50 Km/hr.
Sai ganesh said:
6 years ago
as per my opinion The question is given in m/sec so the answer should be converted into 1 hr = 3600 sec and 1 km = 1000 m.
(3600/1000) m/sec as per given question.
125m and 10 sec,
(125/10)m/sec=45m/sec.
Here the man is moving in the same direction so we should subtract.
(x-5)=45.
x = 50km/hr.
(3600/1000) m/sec as per given question.
125m and 10 sec,
(125/10)m/sec=45m/sec.
Here the man is moving in the same direction so we should subtract.
(x-5)=45.
x = 50km/hr.
Manoj Chauhan said:
1 decade ago
125/10 = 12.5
3600/1000 = 36/10 (you should delete the last two zeros)
36/10 = 3.6
x = 12.5 * 3.6
So that x = 45 per hour right (this is relative speed of train)
x = 45 (you add 5 km per hour for train speed because 45 is relative speed of train).
Therefore x = 50 (the required answer).
3600/1000 = 36/10 (you should delete the last two zeros)
36/10 = 3.6
x = 12.5 * 3.6
So that x = 45 per hour right (this is relative speed of train)
x = 45 (you add 5 km per hour for train speed because 45 is relative speed of train).
Therefore x = 50 (the required answer).
Mohammed Asif said:
3 years ago
The speed of train is 45 km per hour
And relative speed is 50 km per hour.
But in the question only speed of train is asked not the relative speed.
So, please either change the question and mention relative speed or change the answer to option A 45 km per hour which is the speed of train.
And relative speed is 50 km per hour.
But in the question only speed of train is asked not the relative speed.
So, please either change the question and mention relative speed or change the answer to option A 45 km per hour which is the speed of train.
(37)
Sathiyaraj said:
9 years ago
Since train and man run in the same direction,
So, in 10 seconds, train crosees 125 mts (train length) + 125/9 mts,
(5 km/hr => 5000/3600, 10 seconds => 125/9),
So train speed , 36(125 + 125/9) (10 seconds x 36 => 3600 seconds => 1 hr),
Answer : 50, 000 mts = 3600 secs => 50 km/hr.
So, in 10 seconds, train crosees 125 mts (train length) + 125/9 mts,
(5 km/hr => 5000/3600, 10 seconds => 125/9),
So train speed , 36(125 + 125/9) (10 seconds x 36 => 3600 seconds => 1 hr),
Answer : 50, 000 mts = 3600 secs => 50 km/hr.
PKP said:
5 years ago
Wrong solution.
Man also traveled a distance of 5*5/18*10=125/9 m in 10 sec. So this distance should be added to 125 m when calculating relative speed, so relative speed = (125+125/9)/10 = 125/9 m/s = 125/9 * 18/5 km/s = 50 km/hr.
So the speed of the train is 50+5 = 55 km/hr.
Man also traveled a distance of 5*5/18*10=125/9 m in 10 sec. So this distance should be added to 125 m when calculating relative speed, so relative speed = (125+125/9)/10 = 125/9 m/s = 125/9 * 18/5 km/s = 50 km/hr.
So the speed of the train is 50+5 = 55 km/hr.
Mandla npvks said:
10 years ago
Solution: The train length is 125 m.
One man speed is 5 km/h. Time is 10 s.
The velocity of man with respect to train is v=distance/time.
125 m/10 s = 12.5 m/s.
We convert into km/h we multiplied with 18/5.
Then s = 12.5*18/5 = 45 km/h.
The train speed is 45+5 = 50 km/h.
One man speed is 5 km/h. Time is 10 s.
The velocity of man with respect to train is v=distance/time.
125 m/10 s = 12.5 m/s.
We convert into km/h we multiplied with 18/5.
Then s = 12.5*18/5 = 45 km/h.
The train speed is 45+5 = 50 km/h.
Hunt said:
1 decade ago
Relative velocity of train with respect to a fixed point (Let assume a pole).
v = u-5 [u is the velocity of train & 5 is of man & in same direction so negative sign].
Now by simple equation.
Length = Speed x Time.
125 = (u-5*5/18)10.
So u = 250/18 m/s = 50 km/h.
v = u-5 [u is the velocity of train & 5 is of man & in same direction so negative sign].
Now by simple equation.
Length = Speed x Time.
125 = (u-5*5/18)10.
So u = 250/18 m/s = 50 km/h.
Binod verma said:
1 decade ago
When two things are running in the same direction or opposite direction then we say that motion is in relative between them. So at first we find the relative motion and then find the speed of train.
If someone want to find out speed of man that are given in the question.
If someone want to find out speed of man that are given in the question.
Vinothini said:
1 decade ago
Hai friends I want to give small tips.
If there train passes in same direction just subtract it.
If train passes in different or opposite direction direction just add it. If you need to convert km/pr use this formula (a*5%18) for speed and m/sec the formula is (a*18%5).
If there train passes in same direction just subtract it.
If train passes in different or opposite direction direction just add it. If you need to convert km/pr use this formula (a*5%18) for speed and m/sec the formula is (a*18%5).
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