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:
236 comments Page 23 of 24.
Sushma said:
2 decades ago
Thanks Ramakrishna, your answer is excellent.
Y.S.Rama Krishna said:
2 decades ago
Let the speeds of the two trains be x m/sec and y m/sec respectively.
Then, length of the first train = 27x metres,(length=speed*time..so length=x*27=27x metres)
and length of the second train = 17y metres.(length=speed*time..so length=y*17=17y metres)
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.
By using above formula we get d solution for this.
Here it is given that they cross each other in 23 seconds.
So 23 = (27x+17y) / (x+y).
Then, length of the first train = 27x metres,(length=speed*time..so length=x*27=27x metres)
and length of the second train = 17y metres.(length=speed*time..so length=y*17=17y metres)
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.
By using above formula we get d solution for this.
Here it is given that they cross each other in 23 seconds.
So 23 = (27x+17y) / (x+y).
Prabhakaran said:
2 decades ago
Im not clear with above step can anyone give more explanation about this problem. I have doubt in (27x+17y) / (x+y) =23 what this statement mean by. Anyone help me please.
Lokesh said:
2 decades ago
27x - 24x = 23y - 17y
4x = 6y
x/y = 3/2.
4x = 6y
x/y = 3/2.
Bhanu said:
2 decades ago
Take all x terms once side and why terms other side then subtract we get 4x = 6y.
Sameer said:
2 decades ago
Can anyone explain me how he got this step 4x = 6y ?
Sunny(sunil) said:
2 decades ago
http://www.indiabix.com/aptitude/problems-on-trains/formulas
Look at this link then you can understand why we use x+y down there!
Look at this link then you can understand why we use x+y down there!
Vivek said:
2 decades ago
How the (27x+17y)/x+y=23 formula comes?
Mohit sahu said:
2 decades ago
Friends its easy to undrstnd as the qustn says that d trains r moving in oppste drtn that means the total distance travveld by the trains wen they crosses the person will be equal to the total distance travlld by dem in crossng each other.
Mathematly we can also better undrstnd ths by wrtng tht equation as
27x + 17y = 23(x + y).
Mathematly we can also better undrstnd ths by wrtng tht equation as
27x + 17y = 23(x + y).
Arun said:
2 decades ago
Based on the below formula -- >
If two trains of length a(i.e. 27x) metres and b(i.e. 17y) metres are moving in opposite directions at x m/s and y m/s, then:
The time taken by the trains to cross each other (i.e.23 sec) =
(27x + 17y)
```````` secs
(x + y)
Therefore, the above solution is provided based on this derivation. Its given in the formulas section.
If two trains of length a(i.e. 27x) metres and b(i.e. 17y) metres are moving in opposite directions at x m/s and y m/s, then:
The time taken by the trains to cross each other (i.e.23 sec) =
(27x + 17y)
```````` secs
(x + y)
Therefore, the above solution is provided based on this derivation. Its given in the formulas section.
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