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 2 of 6.
MOHANRAJ.A said:
2 decades ago
Assume that length is x meters.
Speed y m/sec, speed=distance/time
so, y=x/15.------------------------1.
Like the same calculate after crossing the platform
y=x+100/25--------------------2
LHS equal. So
x+100/25=x/15;
15(x+100)=25x
Then remaing sme as above.
Speed y m/sec, speed=distance/time
so, y=x/15.------------------------1.
Like the same calculate after crossing the platform
y=x+100/25--------------------2
LHS equal. So
x+100/25=x/15;
15(x+100)=25x
Then remaing sme as above.
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)
ANIL said:
1 decade ago
Nayan correctly said! why they have taken 15 sec for calculating speed of train but not 25 sec? Since distance of signal pole is included in platform, we have to take time taken by train to pass the plateform, and not pole.
Keshab Karmakar said:
1 decade ago
Let trains length is X meter.
When cross the pole the train goes in 1 sec = (100 + X) /25.
When cross the platform the train goes in 1 sec = X/25.
The equation:
(100 + X) /25 = X/25.
X=150.
So the length is 150 m.
When cross the pole the train goes in 1 sec = (100 + X) /25.
When cross the platform the train goes in 1 sec = X/25.
The equation:
(100 + X) /25 = X/25.
X=150.
So the length is 150 m.
Jelli said:
2 decades ago
i think i will try explain simple
1.s=d/t=x(length or distance covered by train)/15
s=x/15
2.the same train to cross cross 100m long platform is
s=d/t
x/15(it's by step1) =(100+x)/25
then we can get x=150m
thank u
1.s=d/t=x(length or distance covered by train)/15
s=x/15
2.the same train to cross cross 100m long platform is
s=d/t
x/15(it's by step1) =(100+x)/25
then we can get x=150m
thank u
Seersha said:
9 years ago
We know, suppose speed = x & length = L.
L/15 = x.
Or L = 15 x.
Now,
(L +100) / 25 = x.
Can we substitute for L here.
(15 x + 100) / 25 = x.
15 x + 100 = 25 x.
100 = 10 x.
X = 10.
L = 15 * 10 = 150.
L/15 = x.
Or L = 15 x.
Now,
(L +100) / 25 = x.
Can we substitute for L here.
(15 x + 100) / 25 = x.
15 x + 100 = 25 x.
100 = 10 x.
X = 10.
L = 15 * 10 = 150.
S Madhukar said:
1 decade ago
Speed = Length/Time.....(1).
Distance = Speed*Time.....(2).
Time = Higher time - Lower time.
= 25-15 = 10.
Distance = 100 given.
100 = Speed*10.
Speed = 10 substitute in equation (1).
Length = 10*15 = 150.
Distance = Speed*Time.....(2).
Time = Higher time - Lower time.
= 25-15 = 10.
Distance = 100 given.
100 = Speed*10.
Speed = 10 substitute in equation (1).
Length = 10*15 = 150.
Anishghoshroy said:
1 decade ago
Let the speed of the train be x.
Then, the length of the train is 15x.
Therefore, 100+15x = 25x.
x = 10.
Which mean the speed of the train is 10 m/s as assumed above.
Then the length of train is 150 m.
Then, the length of the train is 15x.
Therefore, 100+15x = 25x.
x = 10.
Which mean the speed of the train is 10 m/s as assumed above.
Then the length of train is 150 m.
Pavan.k said:
1 decade ago
Let length =x
Case 1: speed of train in 15 sec. =x/15
Case 2: since it crossed pole then the total distance = 100+x
Now speed =100+x/25
Now equating both the speeds x/15 = 100+x/25 we get the x value
Case 1: speed of train in 15 sec. =x/15
Case 2: since it crossed pole then the total distance = 100+x
Now speed =100+x/25
Now equating both the speeds x/15 = 100+x/25 we get the x value
Seema duhan said:
1 decade ago
Let train's length be x meters,
Then, train speed=train length/the time taken to cross the poll.
= x/15.
Train speed=total distance/the time to cross the platform,
x/15 = (x+100)/25.
x = 150.
Then, train speed=train length/the time taken to cross the poll.
= x/15.
Train speed=total distance/the time to cross the platform,
x/15 = (x+100)/25.
x = 150.
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