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 36 of 48.
Pankaj said:
7 years ago
Please explain 5/18 and 18/5.
Why using this?
Why using this?
Phanikumar said:
7 years ago
Speed of the train relative to man = 125/10 m/sec (meters per second).
But you need to find the speed in KMPh.
Ex; 1kmph = 5/18 m/sec,
so that 1m/sec = 18/5 kmph.
Because of that 25/2 is multiplied with 18/5, then we got the speed in KMPh.
Similarly (25/2)*(18/5)=45kmph.
But the both man and train is moving in same direction.
So, X-5=45.
x=50kmph.
But you need to find the speed in KMPh.
Ex; 1kmph = 5/18 m/sec,
so that 1m/sec = 18/5 kmph.
Because of that 25/2 is multiplied with 18/5, then we got the speed in KMPh.
Similarly (25/2)*(18/5)=45kmph.
But the both man and train is moving in same direction.
So, X-5=45.
x=50kmph.
Tanvi said:
7 years ago
Why using 18/5? Please explain.
Narendran Sainathan said:
7 years ago
18/5 is to convert meter per second to kilo meter per hour. Or you can also use 3600 (seconds)/1000 (kilometre).
Omkar tanpure said:
7 years ago
Relative Speed = 45 km/h.
Speed of man = 5 km/h.
But, we know, here,
Relative speed = Speed of train - Speed of the man.
Therefore,
Speed of train = Relative speed + Speed of man.
So, Speed of train = 45 +5 = 50 km/h.
Speed of man = 5 km/h.
But, we know, here,
Relative speed = Speed of train - Speed of the man.
Therefore,
Speed of train = Relative speed + Speed of man.
So, Speed of train = 45 +5 = 50 km/h.
Jola M said:
7 years ago
Converting km/hr to m/s is x*5/18 (For eg, 36 km/hr means 36*5/18 =10 m/s).
Converting m/s to km/hr is x*18/5 (For eg, 10 m/s means 10*18/5= 36 km/hr).
Converting m/s to km/hr is x*18/5 (For eg, 10 m/s means 10*18/5= 36 km/hr).
Rohit said:
7 years ago
Whenever we have to convert seconds or minutes to an hour then multiply by 18/5 and if to do vice versa then 5/18.
Abdus salam said:
7 years ago
Thanks a lot for all the given explanation.
Swati warang said:
7 years ago
What is relative speed, can you explain in simple terms?
Ganesh said:
7 years ago
They asked the train speed; but why we have to take relative speed?
Please tell me.
Please tell me.
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