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 13 of 48.
Sanya said:
1 decade ago
relative speed when two movable things whose speeds x,y are moving in same direction is =X-Y,
relative speed when two movable things whose speeds x,y are moving in OPPOSITE direction is =X+Y
Its an standard formula
relative speed when two movable things whose speeds x,y are moving in OPPOSITE direction is =X+Y
Its an standard formula
Susmitha said:
1 decade ago
x-5 is nothing but here x refers to the speed of train and as both train and boy are moving in the same direction relative velocity comes into picture and here relative velocity is the difference of two velocities.
Kumud Singh said:
7 years ago
1 km = 1000 meters.
1 hr = 3600 seconds.
1 km/hr = 1000/3600 m/s.
= 10/36 m/s.
= 5/18 m/s.
@Gilbert & Dk Singh.
Therefore 1 km/hr = 5/18 m/sec.
Similarly, the reciprocal of m/sec is used to calculate km/hr.
1 hr = 3600 seconds.
1 km/hr = 1000/3600 m/s.
= 10/36 m/s.
= 5/18 m/s.
@Gilbert & Dk Singh.
Therefore 1 km/hr = 5/18 m/sec.
Similarly, the reciprocal of m/sec is used to calculate km/hr.
PANKAJ BARWAL said:
9 years ago
@John.
To convert km/h into m/sec we multiply speed by 5/18.
Because 1km = 1000m &1hour = 3600 sec.
Therefore 1000/3600 = 5/18.
And also for convert m/sec into km/h we multiply speed by 18/5.
3600/1000 = 18/5.
To convert km/h into m/sec we multiply speed by 5/18.
Because 1km = 1000m &1hour = 3600 sec.
Therefore 1000/3600 = 5/18.
And also for convert m/sec into km/h we multiply speed by 18/5.
3600/1000 = 18/5.
Ambikun said:
1 decade ago
There is no need of calculating relative speed. It can be solved easily by calculating the distance traveled by the man in 10 sec and the total distance covered by the train in the same time. This is very simple.
Suraj kale said:
4 years ago
The object Man is also moving in the same direction as that of the train so the total distance covered should not be 125 meters.
It should be the (125+X).
Where X is the distance covered by man in 10 seconds.
It should be the (125+X).
Where X is the distance covered by man in 10 seconds.
Swapnil....... said:
1 decade ago
Why is it addition of 45km/hr & 5km/hr?
Because I thing train & man is going to same direction that time sutract but in this case addition of 45km/Hr & 5km/hr please explain it why is it addition.
Because I thing train & man is going to same direction that time sutract but in this case addition of 45km/Hr & 5km/hr please explain it why is it addition.
Vandna said:
1 decade ago
Can anyone solve this?
A train moving at 36Kmph takes 12 seconds to cross a platform. It takes 6 seconds to cross a man running at the rate of 9Kmph in the opposite direction. Find the length of the train.
A train moving at 36Kmph takes 12 seconds to cross a platform. It takes 6 seconds to cross a man running at the rate of 9Kmph in the opposite direction. Find the length of the train.
ASHUTOSH MAURYA said:
1 decade ago
Distance covered by man = 5*5/18*10.
= 250/18 Meter.
Total Distance covered by Train = 125+250/18 = 2500/18 Meter.
So Train speed = (2500/18)/10 Meter/Second.
or = 2500/180*18/5 Km/Hr.
= 50 Km/Hr.
= 250/18 Meter.
Total Distance covered by Train = 125+250/18 = 2500/18 Meter.
So Train speed = (2500/18)/10 Meter/Second.
or = 2500/180*18/5 Km/Hr.
= 50 Km/Hr.
Sankar said:
1 decade ago
Man has traveled 13.8 m in 10 sec.
i.e 5km/hr = 1.38m/s.
1.38*10s=13.8m he has traveled in 10 sec.
So 125m train has passed 13.8m in 10 sec.
So speed of the train is 13.8m/s i.e 49.68km/hr = 50 km/hr.
i.e 5km/hr = 1.38m/s.
1.38*10s=13.8m he has traveled in 10 sec.
So 125m train has passed 13.8m in 10 sec.
So speed of the train is 13.8m/s i.e 49.68km/hr = 50 km/hr.
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