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 17 of 48.
Anish said:
1 decade ago
Hi Manishkumar,Vijaykumarkuppani,Umesh
U hav cleard the points exactly how itz done.
Thanks a lot...
U hav cleard the points exactly how itz done.
Thanks a lot...
Parvez khan said:
1 decade ago
How was the relative speed calculated ?
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.
Sanghaniakshay said:
1 decade ago
Thanks abhishek.
Greeshma reddy said:
1 decade ago
How did this equation x-5=45 form?
PRADYUMNA KUMAR DAS said:
1 decade ago
If the man and train in opposite direction then it relative speed is x+5. And speed is x+5=45. =>x=40. Am I right?
Sada said:
1 decade ago
Any basic formula is there for this problem kindly explain.
Bhavesh sharma/ gadgad786 said:
1 decade ago
Why we are multiplying the 18/5 ?
or we can ask that why we are divide ?
The answer is simple. We are converting the 'kilo-meters/hour' value into 'meters/second'.
Let me explain about converting km/hr into m/s in detail.
1 km = 1000 meters.
1 hr = 3600 seconds.
1 km/hr = 1000/3600 m/s
= 10/36 m/s
= 5/18 m/s.
Therefore 1 km/hr = 5/18 m/sec.
Similarly 60 km/hr = 60 x 5/18 m/sec.
You may ask me, why should I convert it from km/hr to m/sec?
or we can ask that why we are divide ?
The answer is simple. We are converting the 'kilo-meters/hour' value into 'meters/second'.
Let me explain about converting km/hr into m/s in detail.
1 km = 1000 meters.
1 hr = 3600 seconds.
1 km/hr = 1000/3600 m/s
= 10/36 m/s
= 5/18 m/s.
Therefore 1 km/hr = 5/18 m/sec.
Similarly 60 km/hr = 60 x 5/18 m/sec.
You may ask me, why should I convert it from km/hr to m/sec?
Nil said:
1 decade ago
If we convert km/hr into m/sec i.e. 1000/3600 it's come 5/18. So why it is calculation is 125/10*18/5 instead of 5/18?
Ravi said:
1 decade ago
It is given that
Speed of man=5km/hr
Distance travelled by man in 10s=125/9m
Distance travelled by train in 10s= {125+(125/9)}m
Hence
Speed of train = [{125+(125/9)/10]*3600 = 50 km/hr
Speed of man=5km/hr
Distance travelled by man in 10s=125/9m
Distance travelled by train in 10s= {125+(125/9)}m
Hence
Speed of train = [{125+(125/9)/10]*3600 = 50 km/hr
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