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 7 of 48.
M.saravanan said:
2 decades ago
Please explain 18/5.
(1)
Shwetha A V said:
2 decades ago
60*60/1000=18/5
(1)
Saji said:
2 decades ago
18/5 is to convert m/s to km/hr
(1)
Ankita said:
2 decades ago
Why its substracted?
(1)
Gowtham said:
2 decades ago
Hey why we findind relative speed??? They asking only speed na????
(1)
Dattatray said:
2 decades 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)
Abhishek said:
2 decades ago
Distance = time * speed 125 = 10 * speed
distance/time = speed 125/10 = (25/2)m/s = speed
----------------------------------------------------------
Answer should be in km/hr so convert m/s
km = 1000m and hr = 3600s
m = km/1000 and s = hr/3600
m/s = (3600/1000)km/hr
m/s = (18/5)km/hr
----------------------------------------------------------
The condition was speed = (25/2)m/s
= (25/2)(18/5)km/hr
= 45 km/hr
The speed was relative to man so we have taken time in consideration of man
--------------------------------------------------------
See further in in view answer.
----------------------------------------------------------
distance/time = speed 125/10 = (25/2)m/s = speed
----------------------------------------------------------
Answer should be in km/hr so convert m/s
km = 1000m and hr = 3600s
m = km/1000 and s = hr/3600
m/s = (3600/1000)km/hr
m/s = (18/5)km/hr
----------------------------------------------------------
The condition was speed = (25/2)m/s
= (25/2)(18/5)km/hr
= 45 km/hr
The speed was relative to man so we have taken time in consideration of man
--------------------------------------------------------
See further in in view answer.
----------------------------------------------------------
(1)
Shashank shekhar said:
6 years ago
Train crossing a moving object without length in same direction:
Formula is :-
Time=length of train / ( speed of train-speed of object).
10 sec = 125 m/ ( x - 5*5/18).
So, x=125/9 m/sec = 125/9 * 18/5 km/h = 50 km/h.
Formula is :-
Time=length of train / ( speed of train-speed of object).
10 sec = 125 m/ ( x - 5*5/18).
So, x=125/9 m/sec = 125/9 * 18/5 km/h = 50 km/h.
(1)
Nithish raj said:
5 years ago
125/10 is for speed divide by time taken,
And 18/5 is to convert meter to kilometre
So that 125/10 is 25/2.
Multiply 25/2 by 18/5 to get in kilometre so it gets 45km/hr.
And the man running speed is 5km/hrs.
So, 45 + 5 is 50km/hrs.
And 18/5 is to convert meter to kilometre
So that 125/10 is 25/2.
Multiply 25/2 by 18/5 to get in kilometre so it gets 45km/hr.
And the man running speed is 5km/hrs.
So, 45 + 5 is 50km/hrs.
(1)
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
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