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:
234 comments Page 19 of 24.
Yous said:
8 years ago
Why we should divide by x+y?
Ajay said:
8 years ago
We know time=distance/speed,
The first train length = 27x and second train length=17y.
Given that two trains will cross each other in 23 sec,so applying t=d/s formula.
23 = total distance/total speed.
=> 23=27x+17y/x+y.
The first train length = 27x and second train length=17y.
Given that two trains will cross each other in 23 sec,so applying t=d/s formula.
23 = total distance/total speed.
=> 23=27x+17y/x+y.
Mainul bangladesh khilkhet said:
8 years ago
A train length= 27x.
B train length= 17y.
X meter goes for 1 second.
1 ---> 1/x second.
27x ---> 27x/x second.
Again same as; 17y/y second for 17y.
So, {(27x)/x + (17y)/y} second = 23 second.
=> (27x+17y) meter = (23x + 23y) meter.
=> 4x meter = 6y meter.
=> So, ratio of meter x/y = 3/2.
B train length= 17y.
X meter goes for 1 second.
1 ---> 1/x second.
27x ---> 27x/x second.
Again same as; 17y/y second for 17y.
So, {(27x)/x + (17y)/y} second = 23 second.
=> (27x+17y) meter = (23x + 23y) meter.
=> 4x meter = 6y meter.
=> So, ratio of meter x/y = 3/2.
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.
Mrk said:
8 years ago
Yeah, I got it (x+y) say relative speed.
Gowtham said:
8 years ago
Its very shortcut and its very simple.
27 17
2 3
6 4
The ans is 3:2 (or) 6:4.
27 17
2 3
6 4
The ans is 3:2 (or) 6:4.
Anil Bhadani said:
8 years ago
Its very shortcut and its very simple.
27-23 = 4
23-17 = 6
so,4:6 = 2:3 or 3:2 also.
27-23 = 4
23-17 = 6
so,4:6 = 2:3 or 3:2 also.
Hima said:
8 years ago
Ratio of their speed = total distance travelled/total time taken= total speed.
(27x+17 y)/23 = (x+y),
27x+17y = 23x+23y,
4x = 6y,
x/y = 6/4,
3:2.
(27x+17 y)/23 = (x+y),
27x+17y = 23x+23y,
4x = 6y,
x/y = 6/4,
3:2.
RAHUL tulskar said:
8 years ago
Look at this simplest ans.
Take both crossing time as an x y.
27as x 17 as y.
Then,
27x+17y/x+y=23.
27x+17y=23x+23y.
27x-23x=17y-23y.
4x =6y.
Or
XY=4/6or 2/3 get it.
Take both crossing time as an x y.
27as x 17 as y.
Then,
27x+17y/x+y=23.
27x+17y=23x+23y.
27x-23x=17y-23y.
4x =6y.
Or
XY=4/6or 2/3 get it.
Anuj said:
8 years ago
23-27:23-17.
4:6
2:3
4:6
2:3
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