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Aptitude - Problems on Trains - Discussion

Discussion Forum : Problems on Trains - General Questions (Q.No. 4)
Problems on Trains
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:
1 : 3
3 : 2
3 : 4
None of these
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:
237 comments Page 24 of 24.
SAURABH PANDEY said:   11 months ago
Very well done. Thanks.
(7)
Thavapriya A said:   9 months ago
How to solve the following step?

27x+17y =23x+23y.

Could anyone tell me please?
(22)
Dripta Majumdar said:   8 months ago
Why is the length of the platform not taken into consideration? Anyone, please explain to me.
(10)
Anome said:   4 months ago
Very useful. Thanks all.
(7)
ARUN said:   3 months ago
I do not understand this. Please explain to me.
(4)
Student said:   3 months ago
A train takes 27 sec to reach man and 23 sec to cross train B, so the difference is 4 sec
B train takes 17 sec to reach the man and 23 sec to cross train A, so the difference is 6 sec.

Speed is inversely proportional to time, so the ratio of speed is 6:4.
So 3:2 is the answer.
(60)
Venkatesh said:   2 months ago
Let speeds be x and y.
Then, l1 = x * 27.
l2 = y * 17.
Time taken to cross each other = 23 seconds.
=> (l1+l2)/(x+y) = 23 seconds.
=> 27x + 17y = 23x + 23y.
=> x : y = 3:2.
(4)
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