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 47 of 48.
Sreenivas reddy said:
1 decade ago
Yeah superb.
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.
Thilaga said:
1 decade ago
Nice explanation.Thanks.
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
***********
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
Rahul said:
2 decades ago
@ankita
when a man moves in the direction of train, the train speed is decreased by his own speed. If he moves in the opposite directon he finds the train speed to be much greater. So when is moving in the same direction his speed must be subtracted from that of train speed. If he moves in the opposite direction to that of train, then his speed must be added to the train speed.
moving in same directon: SUBTRACT
moving in opposite directon: ADD
when a man moves in the direction of train, the train speed is decreased by his own speed. If he moves in the opposite directon he finds the train speed to be much greater. So when is moving in the same direction his speed must be subtracted from that of train speed. If he moves in the opposite direction to that of train, then his speed must be added to the train speed.
moving in same directon: SUBTRACT
moving in opposite directon: ADD
Rahul said:
2 decades ago
@gowtham
It would be only speed if the man(REFERENCE POINT) was stationary and only the train was moving. Here as both trian and REFERENCE POINT(man) are moving relative motion comes into picture.
It would be only speed if the man(REFERENCE POINT) was stationary and only the train was moving. Here as both trian and REFERENCE POINT(man) are moving relative motion comes into picture.
Vijayagopal said:
2 decades ago
Why 125/10 the 10 is divided 125 please explain it.
(2)
Gowtham said:
2 decades ago
Hey why we findind relative speed??? They asking only speed na????
(1)
Ankita said:
2 decades ago
Why its substracted?
(1)
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