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:
238 comments Page 4 of 24.
Nidhi said:
1 decade ago
Lets speed of 1st train = x and of 2nd = y.
when they cross man then.....
so length of 1st = 27x and second 17y.
total length = 27x + 17y
now when they cross each other in opp direction they take 23 sec and we know when 2 object run in opp direction their rel speed is
speed of 1st + speed of 2nd = x+y so now length = time * speed = 23(x+y)
Compare both :
27x + 17y = 23(x+y)
27x + 17y = 23x + 23y
4x = 6y => x/y = 3/2.
when they cross man then.....
so length of 1st = 27x and second 17y.
total length = 27x + 17y
now when they cross each other in opp direction they take 23 sec and we know when 2 object run in opp direction their rel speed is
speed of 1st + speed of 2nd = x+y so now length = time * speed = 23(x+y)
Compare both :
27x + 17y = 23(x+y)
27x + 17y = 23x + 23y
4x = 6y => x/y = 3/2.
(1)
Kamanulla said:
6 years ago
A = 27 - 23sec = 4sec.
B = 23 - 17sec = 6sec.
A:B = 4:6 = 2:3 in Sec.
A:B = 3:2 in Speed.
B = 23 - 17sec = 6sec.
A:B = 4:6 = 2:3 in Sec.
A:B = 3:2 in Speed.
(1)
K.kiran kumar said:
2 decades ago
I can't get this step
(27x+17y) / (x+y) = 23
Why we have to use this? can any one explain me.
(27x+17y) / (x+y) = 23
Why we have to use this? can any one explain me.
Niveditha said:
2 decades ago
Anyone please help me how this x+y is divided.
Arjun said:
2 decades ago
(27x+17y)/x+y=23 how did used that step?
Janardhan said:
2 decades ago
It's correct method to solve this problem.
Boomathi said:
2 decades ago
very good solution....
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.
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).
Vivek said:
2 decades ago
How the (27x+17y)/x+y=23 formula comes?
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers