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 5 of 24.
Ganapathi said:
7 years ago
Time taken by 1st train is more than the 2nd train then how speed ratio of 1st train is more than second train? I am not getting this. Please tell me.
Kavya said:
7 years ago
Good answer, Thanks @Shyam.
Vidhyadhar said:
7 years ago
Let x=speed of train 1.
And y=speed of train 2.
Our task=x/y.
So, length of 1st train (d1)=x*27(dist=speed*time)
So, 2nd (d2) = y * 17.
Time taken by trains to cross each other =23 sec.
Time =dist/speed.
23=(d1+d2)/x+y.
23=(27*x+17*y)/x+y.
By solving this we get.
Result = x/y = 3/2
And y=speed of train 2.
Our task=x/y.
So, length of 1st train (d1)=x*27(dist=speed*time)
So, 2nd (d2) = y * 17.
Time taken by trains to cross each other =23 sec.
Time =dist/speed.
23=(d1+d2)/x+y.
23=(27*x+17*y)/x+y.
By solving this we get.
Result = x/y = 3/2
Deb said:
7 years ago
We can solve by (27-23)/(23-17).
Swaminathan said:
7 years ago
Hi,
According to me,
(27-23): (17-23),
4 : 6.
Am I right?
According to me,
(27-23): (17-23),
4 : 6.
Am I right?
Ramhari said:
7 years ago
In this question, there is no any data that two trains are equal length. A train has passed a man in 27 seconds and another has passed in 17. The second one might be faster or short in length. So, Both can happen.
Rekha Kondamangale said:
7 years ago
Formula is
The ratio of speed = ax+by /x+y.
The ratio of speed = ax+by /x+y.
Shree said:
7 years ago
Thanks for explaining the answer. It's easy to understand the solution now.
Manish said:
7 years ago
27 and 17 are the length of the train and the speed of these train respectively x mtr/sec and y mtr/sec.
So 27x+17x are there relative speed of the train.
(27x+17y)/(x+y)=23.
Here 23 is given time in which the Cross each other's train after solving the above eq...
We get 4x=6y.
x/y=2/3 that's solved.
So 27x+17x are there relative speed of the train.
(27x+17y)/(x+y)=23.
Here 23 is given time in which the Cross each other's train after solving the above eq...
We get 4x=6y.
x/y=2/3 that's solved.
L.santhosh reddy said:
7 years ago
Here, they mentioned 23sec and17sec but in answer, they took it as 23m and 17m why?
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