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:
476 comments Page 18 of 48.
Gogul prasath said:
1 decade ago
Relative speed is difference between speed of train and speed of man.
x: Speed of train.
5: Speed of man.
Difference is (x-5) = 45.
45 is relative speed.
x: Speed of train.
5: Speed of man.
Difference is (x-5) = 45.
45 is relative speed.
Sohail said:
1 decade ago
Why did you put 18/5 instead 5/18?
Where 5 denotes the meter and 18 denotes the hours (1000/3600) this should be as (25/2 x 5/18)?
I am a little unclear.
Where 5 denotes the meter and 18 denotes the hours (1000/3600) this should be as (25/2 x 5/18)?
I am a little unclear.
Ahmed said:
1 decade ago
Explanation given by ramesh chandra is very good and short, Please follow his process without wasting your time.
We need such a good explanation like that.
We need such a good explanation like that.
KAushiK said:
10 years ago
I have a doubt were in some case we consider 18/5 and in some case we consider 5/18?
Can anyone please let me know in which of the cases we consider what?
Can anyone please let me know in which of the cases we consider what?
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).
Siddharth said:
6 years ago
We 1st Find the speed of train relative to man Vr.
Man and train moved in the same direction = (V-U).
V = Speed of the train.
U = Speed of man.
Vr = (V-U).
Man and train moved in the same direction = (V-U).
V = Speed of the train.
U = Speed of man.
Vr = (V-U).
Aditya said:
1 decade ago
The train and man are moving in the same direction so. If we want to take out the speed of any one of them, then we have to take one object as stationery.
Moustafa Elhosiny said:
1 year ago
Sp of man = 5 * 5/18
= 25/18 m/sec.
Let Sp of train be x, then;
x - 25/18 = 125/10
So x = 125/10 + 25/18 = 125/9 m/sec.
So x = 125/9 * 18/5 =50 Km/h.
= 25/18 m/sec.
Let Sp of train be x, then;
x - 25/18 = 125/10
So x = 125/10 + 25/18 = 125/9 m/sec.
So x = 125/9 * 18/5 =50 Km/h.
(49)
Sathish said:
1 decade ago
(x-5) is not a standard formula x is taken as speed of train and 5 is man's speed, to calculate train's speed from relative speed we subtract (x-5).
Atharv S Shelar said:
2 years ago
@All.
All asking the same doubt "why it is 18/5 and not 5/18"?
It is because the conversion for m/s to km/hr is 18/5 and for km/hr to m/s is 5/18.
All asking the same doubt "why it is 18/5 and not 5/18"?
It is because the conversion for m/s to km/hr is 18/5 and for km/hr to m/s is 5/18.
(53)
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