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 44 of 48.
Saranya said:
1 decade ago
hai raghu, in the question man's speed is given in km/hr so we gonna convert train's speed to km/hr which is actually in m/s
1 m/s = 3600 km/1000 hr
125/10 m/s= (125/10)*(3600/1000)
1 m/s = 3600 km/1000 hr
125/10 m/s= (125/10)*(3600/1000)
Raghu said:
1 decade ago
How it is 3600/1000. It will come as 1000/3600 only. Please explain.
Prithika said:
1 decade ago
@kumar
cause speed=distance/time
cause speed=distance/time
Kumar said:
1 decade ago
Why 125 is divided by 10?
Kannips said:
1 decade ago
speed=distance/time.so speed=125/10.....25/2*18/5=45... the question is same direction=x-5=45 x=50
Jelli said:
1 decade ago
Thanks to all.
I got many idea's to solve this problem.
I got many idea's to solve this problem.
Priyavel said:
1 decade ago
Both (train and man) moves in same direction so we subtract.
Both moves in opposite direction means we add it.
We convert m into km, sec into hour so we multiply 18/5.
Both moves in opposite direction means we add it.
We convert m into km, sec into hour so we multiply 18/5.
Nas said:
1 decade ago
Nice explanation friends. !
Vijay kumar kuppani said:
1 decade ago
DONT WORRY FRIENDS ITS VERY SIMPLE
instead of going for a new formula.we can simply get the answer by using the standard formula.i,e
t=(a+b)/(u-v)
u can see this formula from the general formulas of this exercise.
where
t-time taken by the train to cross the man=10 sec;
a-length of the train=125meters;
b=0(because the train is supposed to cross a person);
u=speed of the train(you are supposed to find out);
v=speed of the man who is running=5km/hr=5*(5/18)=25/18m/sec;
by substituting the values in the above equation you can get the value..
instead of going for a new formula.we can simply get the answer by using the standard formula.i,e
t=(a+b)/(u-v)
u can see this formula from the general formulas of this exercise.
where
t-time taken by the train to cross the man=10 sec;
a-length of the train=125meters;
b=0(because the train is supposed to cross a person);
u=speed of the train(you are supposed to find out);
v=speed of the man who is running=5km/hr=5*(5/18)=25/18m/sec;
by substituting the values in the above equation you can get the value..
Onam said:
1 decade ago
5/18 is conversion of km/hr to m/s and 18/5 is conversion digit m/s to km/s
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