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 1 of 6.
Gautam said:
4 months ago
Let the length of the train = x.
Now,
(X+100)/25 = X/15,
Then, X = 150.
Now,
(X+100)/25 = X/15,
Then, X = 150.
(1)
Gautam Kumar Ray said:
4 months ago
We know S = D/T,
for train S = D/15,
Now,
D/15 = (D+100)/25,
3D + 300 = 5D,
D = 150.
for train S = D/15,
Now,
D/15 = (D+100)/25,
3D + 300 = 5D,
D = 150.
(1)
Arun said:
11 months ago
Every question they used the word " cross the pole" but here they mention " past the pole " (mean we need to reduce the time from the platform).
So time has been 25-15 = 10, T = 10.
S = 100m/10sec = 10m/sec.
S = D/T.
x + D = S*T,
X + 100 = 10* 25,
x+100 = 250,
x = 250-100,
x = 150.
So time has been 25-15 = 10, T = 10.
S = 100m/10sec = 10m/sec.
S = D/T.
x + D = S*T,
X + 100 = 10* 25,
x+100 = 250,
x = 250-100,
x = 150.
(7)
Bir bdr said:
2 years ago
Let length of train = x m.
From 1st case.
Speed = x/15.
From the Second case;
speed = x + 100/25.
Now x/15 = x + 100/25.
25x = 15x + 1500.
10x = 1500.
x = 150 m.
From 1st case.
Speed = x/15.
From the Second case;
speed = x + 100/25.
Now x/15 = x + 100/25.
25x = 15x + 1500.
10x = 1500.
x = 150 m.
(5)
Shubham lad said:
3 years ago
Can we calculate the speed of the train 100/25=4 m/s and length = 15 * 4 = 60m?
Please explain.
Please explain.
(5)
Gugi said:
5 years ago
Explain the answer, please.
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)
Debdiya said:
5 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)
Sahil chabra said:
5 years ago
Can anyone explain the below step in detail?
(100+x) /25=x/15.
(100+x) /25=x/15.
(3)
Madhan said:
5 years ago
Thanks all.
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