Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 19)
19.
A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is:
Answer: Option
Explanation:
Let the length of the train be x metres and its speed by y m/sec.
| Then, | x | = 15  y = |
x | . |
| y | 15 |
 |
x + 100 | = | x |
| 25 | 15 |
15(x + 100) = 25x
15x + 1500 = 25x
1500 = 10x
x = 150 m.
Discussion:
55 comments Page 5 of 6.
Mr.N.P. said:
7 years ago
Time Difference of Platform and Pole = 25-15= 10s.
Platform is 100m long.
speed of Train is = (D/T)=(100/10) =10m/s.
Length of pole(Train) = S * T = 10 * 15 = 150m.
Platform is 100m long.
speed of Train is = (D/T)=(100/10) =10m/s.
Length of pole(Train) = S * T = 10 * 15 = 150m.
(1)
Arjun said:
6 years ago
Let x be the length of train.
Therefore speed of train = x/15 m/sec.
x+100 = (x/15) m/sec * 25 sec.
3x+300 = 5x.
x = 300/2 =150 m.
Therefore speed of train = x/15 m/sec.
x+100 = (x/15) m/sec * 25 sec.
3x+300 = 5x.
x = 300/2 =150 m.
Zeeshan said:
6 years ago
In very simple form:
First calculate the speed relative to platform S=D/T.
S= 100/(25-15).
S= 10m/s.
Now as S = D/T so D= S*T.
D = 10*15= 150m which is relative to Pole.
Or
D= 10*25= 250 which is relative to platform so subtract length of Platform D= 250- 100= 150m.
First calculate the speed relative to platform S=D/T.
S= 100/(25-15).
S= 10m/s.
Now as S = D/T so D= S*T.
D = 10*15= 150m which is relative to Pole.
Or
D= 10*25= 250 which is relative to platform so subtract length of Platform D= 250- 100= 150m.
(11)
Sia Siam Changsan said:
6 years ago
Let x meter be the length of the train.
We have, speed = distance/time.
S=x/15 ( to pole),
Again, s=d/t,
x/15= x+100/25(to platform),
x=150m.
We have, speed = distance/time.
S=x/15 ( to pole),
Again, s=d/t,
x/15= x+100/25(to platform),
x=150m.
(3)
Sanjana said:
6 years ago
Good explanation.
Madhan said:
6 years ago
Thanks all.
Sahil chabra said:
6 years ago
Can anyone explain the below step in detail?
(100+x) /25=x/15.
(100+x) /25=x/15.
(3)
Debdiya said:
6 years ago
100 + x is the total length.
See, x is the length of the train which is assumed.
Length of the platform - 100 m,
So, 100 + x is the total length.
And as we know;
Distance = speed x time.
And speed = distance by time.
I think this helps you all.
See, x is the length of the train which is assumed.
Length of the platform - 100 m,
So, 100 + x is the total length.
And as we know;
Distance = speed x time.
And speed = distance by time.
I think this helps you all.
(1)
Suraj said:
5 years ago
In 15 sec it crosses poll and in 25 sec it crosses the platform. Hence time to cover platform will be 25-15=10 secs.
Hence from poll to crossing the platform the length of the train will be equal to the platform which is 100m.
Now,
We need to calculate its speed:
Xkmh in 36sec.
100mtrs in 10 sec.
Then X=(36*100)/10 = 36 kmph.
Now the actual length of the train
360 mtrs in 36 secs.
X meter in 15 sec.
X = (360*15)/36 which will give you 150mtrs.
Hence from poll to crossing the platform the length of the train will be equal to the platform which is 100m.
Now,
We need to calculate its speed:
Xkmh in 36sec.
100mtrs in 10 sec.
Then X=(36*100)/10 = 36 kmph.
Now the actual length of the train
360 mtrs in 36 secs.
X meter in 15 sec.
X = (360*15)/36 which will give you 150mtrs.
(1)
Gugi said:
5 years ago
Explain the answer, please.
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