Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 4)
4.
Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is:
Answer: Option
Explanation:
Let the speeds of the two trains be x m/sec and y m/sec respectively.
Then, length of the first train = 27x metres,
and length of the second train = 17y metres.
 |
27x + 17y | = 23 |
| x+ y |
27x + 17y = 23x + 23y
4x = 6y
| |
x | = | 3 | . |
| y | 2 |
Discussion:
233 comments Page 9 of 24.
Kartik said:
8 years ago
Alternative solution.
Simplest of all,
Train a passes the object at 27 sec.
Train b passss at 17 sec.
They cross each other at 23 sec.
Hence ,
23-17 = 6.
27-23 = 4.
Hence,
Ratio will be 6:4 or 3:2.
Simplest of all,
Train a passes the object at 27 sec.
Train b passss at 17 sec.
They cross each other at 23 sec.
Hence ,
23-17 = 6.
27-23 = 4.
Hence,
Ratio will be 6:4 or 3:2.
Anjan kumar said:
1 decade ago
@k.kiran kumar
27x+17y/x+y
here as the two trains cross each other total distance they travelled is length of them.As given in problem they cross in 23 seconds.
time=distance/speed
i.e 23=27x+17y/x+y
27x+17y/x+y
here as the two trains cross each other total distance they travelled is length of them.As given in problem they cross in 23 seconds.
time=distance/speed
i.e 23=27x+17y/x+y
Riyas said:
1 decade ago
My explain,
You know 2train x and y
crossing the time =27then17 so 27x 17y
Given
Then each other train crossing 23 second.
so 23x 23y
27x+17y=23x+23y
27x-23x=23y-17y
Tf 4x=6y
x=6y/4
x/y=6/4
=3/2
You know 2train x and y
crossing the time =27then17 so 27x 17y
Given
Then each other train crossing 23 second.
so 23x 23y
27x+17y=23x+23y
27x-23x=23y-17y
Tf 4x=6y
x=6y/4
x/y=6/4
=3/2
Vijendra said:
9 years ago
The speeds of trains should be added because they are moving in opposite direction.
-------------> man < ----------------.
The speeds of both trains contributing to finish it in 23 seconds.
-------------> man < ----------------.
The speeds of both trains contributing to finish it in 23 seconds.
Gulshan said:
1 decade ago
Here concept of relative velocity is used.
When objects move opposite to each other, their speed is added and when they move in same direction speed is the difference of their respective speeds.
When objects move opposite to each other, their speed is added and when they move in same direction speed is the difference of their respective speeds.
Dileep said:
1 decade ago
If Two trains of length a metres and b metres are moving in opposite directions at u m/s and v m/s, then the time taken by the trains to cross each other=(a+b)/(u+v)sec.
a=27x, b=27y, u=x, v=y.
a=27x, b=27y, u=x, v=y.
R.Abiraman said:
1 decade ago
Relative speed of train = x+y;
Train 1 dis = 27x;
Train 2 dis = 17y;
Formula(speed = distance/time).
So x+y = (27x+17y)/23.
23x+23y = 27x+17y;
-4x+6y = 0;
6y = 4x;
x/y = 6/4.
So 3:2.
Train 1 dis = 27x;
Train 2 dis = 17y;
Formula(speed = distance/time).
So x+y = (27x+17y)/23.
23x+23y = 27x+17y;
-4x+6y = 0;
6y = 4x;
x/y = 6/4.
So 3:2.
Yarasani srinivas said:
9 years ago
TIME = DISTANCE /SPEED.
We don't know how much distance apart.
27x is train1 distance at which it crosses man.
17y is a 2nd train.
We know when they meet 23 sec.
23 = 27x + 17y/ x + y.
We don't know how much distance apart.
27x is train1 distance at which it crosses man.
17y is a 2nd train.
We know when they meet 23 sec.
23 = 27x + 17y/ x + y.
Sarat said:
9 years ago
TIME = DISTANCE /SPEED.
We don't know how much distance apart
27x is train1 distance at which it crosses man
17y is 2nd train.
We know when they meet 23 sec.
23 = 27x + 17y/ x + y.
We don't know how much distance apart
27x is train1 distance at which it crosses man
17y is 2nd train.
We know when they meet 23 sec.
23 = 27x + 17y/ x + y.
Vadivel said:
1 decade ago
Why should both trains have different length. Even sometimes they can have same length and can run in different speeds right. Then how can we do like that. Can anyone explain please?
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