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 18 of 48.
Shailesh said:
1 decade ago
Speed of train=(length of train/time) is a formula
hence,
125/10 m/sec
now (125/10)*(18/5)=45.. multiply by 18/5 to become km/h
now 45 is relative speed
sr=s1-s2
45=s1-5
s1=50
hence,
125/10 m/sec
now (125/10)*(18/5)=45.. multiply by 18/5 to become km/h
now 45 is relative speed
sr=s1-s2
45=s1-5
s1=50
Chandu said:
1 decade ago
Why it is subtracted ? please explain.
Vikram said:
1 decade ago
A Train 125m long passes a man,running at 5km/hr.
It means that train speed =5000m/3600sec.------(1hr=60*60=3600sec & 1km=1000meters).
& Second Train running on same Direction & Passed in 10sec's.
It means Second train cross distance within 10sec's.
Speed of Train for meters/10sec = 5000m/3600sec*10sec=1.388888888889m
So,that train speed for km/hr=speed of train for 10 sec * remaining 3590 Seconds(3600-10).
=1.3888888889*3590=49.8611111111111111=50km/hr.
Therefore, A speed of that train=50km/hr.
It means that train speed =5000m/3600sec.------(1hr=60*60=3600sec & 1km=1000meters).
& Second Train running on same Direction & Passed in 10sec's.
It means Second train cross distance within 10sec's.
Speed of Train for meters/10sec = 5000m/3600sec*10sec=1.388888888889m
So,that train speed for km/hr=speed of train for 10 sec * remaining 3590 Seconds(3600-10).
=1.3888888889*3590=49.8611111111111111=50km/hr.
Therefore, A speed of that train=50km/hr.
Bulldozzer said:
1 decade ago
This is simple. Length of the train is given and the seconds is given.
So we have m/sec there. To convert it to km/hr,
1km= 1000 m and 1 hr = 3600 sec.
So km/hr= 1000/3600. So we have 18/5. Now we got our km/hr.
Well that guy is running at 5 km speed. So we take the train speed as x and subtracting the 5 km speed from that. We have x-5 as the train speed. Now x-5= 45. So x= 45+5=50. :-).
So we have m/sec there. To convert it to km/hr,
1km= 1000 m and 1 hr = 3600 sec.
So km/hr= 1000/3600. So we have 18/5. Now we got our km/hr.
Well that guy is running at 5 km speed. So we take the train speed as x and subtracting the 5 km speed from that. We have x-5 as the train speed. Now x-5= 45. So x= 45+5=50. :-).
Kishore Kumar said:
1 decade ago
Your running at a speed of 5km/hr
(1km=1000 meter and 1hr=3600seconds,which will be 1000/3600=10/36=5/18)
Note :for 1 km/hr
Therefore 5(given km)*5/18=1.39
-------------------------------
Meanwhile 125m long train crosses you in 10 seconds along with you in same diretion.
Then!!
125/10 i.e its in the form of (125)m/(10)s.
-------------------------------
So add those two values in the form of m/s,which is 13.89=a
-------------------------------
Now question to find speed of the train,since we found in the form of m/s,but the options provided are in the form of KM/HR
-------------------------------
So to convert M/S to KM/HR :
(a*18/5)=(13.89*3.6)
Gives answer as 50 km/hr
(1km=1000 meter and 1hr=3600seconds,which will be 1000/3600=10/36=5/18)
Note :for 1 km/hr
Therefore 5(given km)*5/18=1.39
-------------------------------
Meanwhile 125m long train crosses you in 10 seconds along with you in same diretion.
Then!!
125/10 i.e its in the form of (125)m/(10)s.
-------------------------------
So add those two values in the form of m/s,which is 13.89=a
-------------------------------
Now question to find speed of the train,since we found in the form of m/s,but the options provided are in the form of KM/HR
-------------------------------
So to convert M/S to KM/HR :
(a*18/5)=(13.89*3.6)
Gives answer as 50 km/hr
Sunil said:
1 decade ago
How/ why Let the speed of the train be x km/hr. Then, relative speed = (x - 5) km/hr.
Please any one explain me why let speed =(x-5)km hr.
Please any one explain me why let speed =(x-5)km hr.
Harish said:
1 decade ago
It is brain storming and conceptual question .Thank you for giving more explanation on this question.Thank you very much....!
Karthik said:
1 decade ago
125/10 = 25/2
25/2*18/5 = 450/10
45
friends,
i don't know how to solve this problems after this
so plz anyone help me out
25/2*18/5 = 450/10
45
friends,
i don't know how to solve this problems after this
so plz anyone help me out
Anbu said:
1 decade ago
Just try this 1 sec 5 km/hr means 10 sec is 50 km/hr thats it..
becoz the man running at same time train is moving ..
becoz the man running at same time train is moving ..
Mamatha said:
1 decade ago
To convert km/h into m/s we multiply that value with 5/18.why is this because
1km=1000m
1h=60min*60sec=3600sec
now
1km/h=1000/3600=5/18
if we want to convert m/s into km/h we have to multiply with 18/5.
hope you can understand.
1km=1000m
1h=60min*60sec=3600sec
now
1km/h=1000/3600=5/18
if we want to convert m/s into km/h we have to multiply with 18/5.
hope you can understand.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers