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 2 of 48.
Rahul said:
2 decades ago
@ vijayagopal
here both man and train are moving in the same direction and the train crosses the man in 10 seconds.
speed = distance(or length)/time.
As both man and train are moving, relative motion comes into picture.
therefore:
relative speed= (length of the train)/(time taken by the train to cross the man who is in motion)
relative speed= 125/10
here both man and train are moving in the same direction and the train crosses the man in 10 seconds.
speed = distance(or length)/time.
As both man and train are moving, relative motion comes into picture.
therefore:
relative speed= (length of the train)/(time taken by the train to cross the man who is in motion)
relative speed= 125/10
N Ramesh Chandra said:
1 decade ago
Hai Madhu N Swathi,
****When two bodies say x km/hr and y km/hr are moving in the same direction then their relative speed is (x-y) km/hr
****When we want to convert km/hr in to m/s we multiply with 5/18.
*** Let the speed of the train be x kmph
Speed of the train relative to man(x-5)kmph
(x-5)*5/18
now as we know that Distance/speed=time
now,speed is (x-5)*5/18;
distance is 125m;
time is 10 sec;
now u vl get the answer
***********
****When two bodies say x km/hr and y km/hr are moving in the same direction then their relative speed is (x-y) km/hr
****When we want to convert km/hr in to m/s we multiply with 5/18.
*** Let the speed of the train be x kmph
Speed of the train relative to man(x-5)kmph
(x-5)*5/18
now as we know that Distance/speed=time
now,speed is (x-5)*5/18;
distance is 125m;
time is 10 sec;
now u vl get the answer
***********
Thilaga said:
1 decade ago
Nice explanation.Thanks.
Umair chudhary said:
1 decade ago
If someone feel difficult to understand 5/18 i.e; m/s
To convert kmph to mps 1000/60*60 m/s
It is same thing.
To convert kmph to mps 1000/60*60 m/s
It is same thing.
Sreenivas reddy said:
1 decade ago
Yeah superb.
Kamalakannan said:
1 decade ago
Answer = 45 km/hr is relative speed of the train.
Now, you calculate (u-v).
The Speed of the train 50 km/hr answer is correct.
Now, you calculate (u-v).
The Speed of the train 50 km/hr answer is correct.
Antony said:
1 decade ago
Please explain 18/5.
Dattatray said:
1 decade ago
18/5 = 1 km/hr = 1000/3600 m/s
= 10/36 m/s
= 5/18 m/s.
= 10/36 m/s
= 5/18 m/s.
(1)
Sheela said:
1 decade ago
1km=1000m.
1hour=3600sec.
So to convert from km/hr to m/sec, we need to divide 3600/1000 i.e,.
1km/1hr=3600s/1000m which is equal to 18/5.
If it was asked to convert m/s to km/hr then it would be 1000m/3600s= 5/18
1hour=3600sec.
So to convert from km/hr to m/sec, we need to divide 3600/1000 i.e,.
1km/1hr=3600s/1000m which is equal to 18/5.
If it was asked to convert m/s to km/hr then it would be 1000m/3600s= 5/18
Saranya said:
1 decade ago
I could not understand this problem is there any way to understand this more easily.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers