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:
478 comments Page 5 of 48.
Sunil said:
2 years ago
First, let's convert man running speed into second.
5000 ÷ 3600 = 1.38888.
3600 second is equal to 1hr.
1.38888 × 10 second
Why we multiply because we want to know how much the man covered meters in 10 seconds.
So the man covered in 10sec..
Is that 13.88888 then let's multiply.
13.8888×3600 = 50,000 meter
(3,600 is second)
Convert meter into km.
50,000÷1000= 50km.
The answer is 50km train speed.
5000 ÷ 3600 = 1.38888.
3600 second is equal to 1hr.
1.38888 × 10 second
Why we multiply because we want to know how much the man covered meters in 10 seconds.
So the man covered in 10sec..
Is that 13.88888 then let's multiply.
13.8888×3600 = 50,000 meter
(3,600 is second)
Convert meter into km.
50,000÷1000= 50km.
The answer is 50km train speed.
(61)
Baji said:
10 years ago
Here the time 10 seconds is the time taken by the train to cross it's one length and the person running distance in 10 seconds.
So the travelled distance of the person in 10 seconds is = 5 km/hr*5/18*10 = 13.8888 mts.
And the train distance is 125 mts.
The total distance is = 138.88888.
So the finally the velocity of train is 138.8888/10.
= 13.8888888 mts/sec.
= 13.888888*18/5.
= 50 km/hr.
So the travelled distance of the person in 10 seconds is = 5 km/hr*5/18*10 = 13.8888 mts.
And the train distance is 125 mts.
The total distance is = 138.88888.
So the finally the velocity of train is 138.8888/10.
= 13.8888888 mts/sec.
= 13.888888*18/5.
= 50 km/hr.
Bulldozzer said:
1 decade ago
This is simple. Length of the train is given and the seconds is given.
So we have m/sec there. To convert it to km/hr,
1km= 1000 m and 1 hr = 3600 sec.
So km/hr= 1000/3600. So we have 18/5. Now we got our km/hr.
Well that guy is running at 5 km speed. So we take the train speed as x and subtracting the 5 km speed from that. We have x-5 as the train speed. Now x-5= 45. So x= 45+5=50. :-).
So we have m/sec there. To convert it to km/hr,
1km= 1000 m and 1 hr = 3600 sec.
So km/hr= 1000/3600. So we have 18/5. Now we got our km/hr.
Well that guy is running at 5 km speed. So we take the train speed as x and subtracting the 5 km speed from that. We have x-5 as the train speed. Now x-5= 45. So x= 45+5=50. :-).
Qasim said:
4 years ago
The train and the man are moving in the same direction we have to use subtraction.
Here, we have to find the value of X. So for that, we have to keep X separate either left side or right.
Shift 45 to left and x to right. Because we are shifting, the sign will be change (positive to negative & negative to positive).
x-5 = 45
-5 - 45 = -x
-50 = -x ....(- - = + , so - - canceled)
x = 50.
Here, we have to find the value of X. So for that, we have to keep X separate either left side or right.
Shift 45 to left and x to right. Because we are shifting, the sign will be change (positive to negative & negative to positive).
x-5 = 45
-5 - 45 = -x
-50 = -x ....(- - = + , so - - canceled)
x = 50.
Chandan said:
1 decade ago
60min -> 5km.
1min->? =>(1*5)/60 = 1/12km.
For 1 second -> (1/12)/60 = 1/720km.
For 10 second ->(1/720)*10 = 1/72km.
It means train covered 1/72km in 10second, then calculate how much distance that train can cover in 60 min(1 hour). Because they've given the choices in km/hr.
=>(1/72)*(60*60)=50km/hr.
Note: Length of the train is not required in the calculation.
1min->? =>(1*5)/60 = 1/12km.
For 1 second -> (1/12)/60 = 1/720km.
For 10 second ->(1/720)*10 = 1/72km.
It means train covered 1/72km in 10second, then calculate how much distance that train can cover in 60 min(1 hour). Because they've given the choices in km/hr.
=>(1/72)*(60*60)=50km/hr.
Note: Length of the train is not required in the calculation.
Rachit said:
8 years ago
RELATIVE SPEED OF TRAIN WITH RESPECT TO MAN RUNNING= (x-5)km/hr.
TIME=DISTANCE/RELATIVE SPEED.
Therefore we know that- to convert km/hr to m/s we have to use,
(x-5) * 5/18)m/sec.
TIME=DISTANCE/RELATIVE SPEED
10=125/(x-5)*5/18.
10=TIME,125=DISTANCE,(x-5)*5/18=RELATIVE SPEED
CALCULATION-
10=125/(x-5)*5/18,
10=125*18/5x-25,
10=2250/5x-25,
10(5x-25)=2250,
50x-250=2250,
50x=2500,
x=50km/hr.
TIME=DISTANCE/RELATIVE SPEED.
Therefore we know that- to convert km/hr to m/s we have to use,
(x-5) * 5/18)m/sec.
TIME=DISTANCE/RELATIVE SPEED
10=125/(x-5)*5/18.
10=TIME,125=DISTANCE,(x-5)*5/18=RELATIVE SPEED
CALCULATION-
10=125/(x-5)*5/18,
10=125*18/5x-25,
10=2250/5x-25,
10(5x-25)=2250,
50x-250=2250,
50x=2500,
x=50km/hr.
Suganthan.M said:
1 decade ago
We need the speed of the train
we have only one clue about the train is 125m and 10s
speed=distance/time
(i.e)125/10= 12.5 m/s
but we need the answer in km/hr so convert it
12.5*(18/5)=12.5*3.6
=45 km/hr almost we got it
then about the direction, it is in same direction
Now the speed of the train as x,
because of same direction subtract it from x
x-5=45
x=45+5
x=50km/hr
we have only one clue about the train is 125m and 10s
speed=distance/time
(i.e)125/10= 12.5 m/s
but we need the answer in km/hr so convert it
12.5*(18/5)=12.5*3.6
=45 km/hr almost we got it
then about the direction, it is in same direction
Now the speed of the train as x,
because of same direction subtract it from x
x-5=45
x=45+5
x=50km/hr
Suresh said:
6 years ago
125m
5km/hr
10sec
Speed=distance/time.
Therefore S=km/hr(it's convert to m/sec)
S=1000m/3600sec
S=5/18.
Therefore S=D/T
D=125m
T=10sec
S=125/10
S=12.5, S=5/18.
Therefore 12.5=5/18=S(cross multiplication)
S = 12.5 * 18/5.
S = 225/5,
S = 45km/hr.
Remaining train running speed is added.
Therefore S = 45 + 5.
= 50km/hr.
5km/hr
10sec
Speed=distance/time.
Therefore S=km/hr(it's convert to m/sec)
S=1000m/3600sec
S=5/18.
Therefore S=D/T
D=125m
T=10sec
S=125/10
S=12.5, S=5/18.
Therefore 12.5=5/18=S(cross multiplication)
S = 12.5 * 18/5.
S = 225/5,
S = 45km/hr.
Remaining train running speed is added.
Therefore S = 45 + 5.
= 50km/hr.
CHINNU said:
9 years ago
Here, one thing I got to know is that, you all have missed a point and that was making a sense and hence considerable.
We can assume a stationary man or a pole of negligible length but this man was moving with a speed of 5km/hr and hence covered almost (10 * (5 * 5/18)) meters in 10 seconds and so the length should be considered. Thus the answer is 55Km/hr instead of 50Km/hr.
We can assume a stationary man or a pole of negligible length but this man was moving with a speed of 5km/hr and hence covered almost (10 * (5 * 5/18)) meters in 10 seconds and so the length should be considered. Thus the answer is 55Km/hr instead of 50Km/hr.
Berman said:
2 years ago
Distance covered in crossing.
When the train crosses a stationary object or pole or another train.
The distance covered by the train = length of the train.
So, the length of the train is 125 m =distance covered by the train.
and we know that it took 10 sec to pass the man.
Train Speed = speed of man*time taken by the train to pass,
Speed = 5km/hr * 10sec.
Speed = 50km/hr.
When the train crosses a stationary object or pole or another train.
The distance covered by the train = length of the train.
So, the length of the train is 125 m =distance covered by the train.
and we know that it took 10 sec to pass the man.
Train Speed = speed of man*time taken by the train to pass,
Speed = 5km/hr * 10sec.
Speed = 50km/hr.
(264)
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers