Aptitude - Problems on Trains - Discussion

27            17
      23
23-17=6          27-23=4

Then ratio become 3:2

Hi Lokesh,

Can you please explain why you've said 27x-24x=23y-17y.....?


I can't see figure of 24 ain't where???

Thanks in advance....

Thanks Y.S.Rama Krishna

I understood the answer now. :)

@ chanti
its length=speed*time
so length of first train=27*x mts
and length of 2nd train= 17*y mts

The 1st train sec 27-23=4.

The 2nd train sec 23-17=6.

So both are divide by 2.

4/2=2, and 6/3=3.

So the ratio is 3:2 its right method?

I think I am contented with fathima explanation thank you all.

I can't get this step

(27x+17y) / (x+y) = 23

Why we have to use this? can any one explain me.

Let Speed of Train A= x m/s
And Speed of Train B= y m/s

Time taken by Train A to cover distance equals to its length = 27 s

Time taken by Train B to cover distance equals to its length = 17 s

Total distance covered
---------------------- = Time taken to Cross each other
Total speed


(Length of train A)+ (Length of train B)
so, --------------------------------------- = 23 seconds
(Speed of train A) + (Speed of train B)

(Speed x time) of Train A + (Speed x time) of Train B
----------------------------------------------------- =23
(Speed of train A) + (Speed of train B)

27x + 17y
--------- = 23
x + y

27x + 17y = 23x + 23y
4x =6y

x/y= 3/2

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.

a=27x, b=27y, u=x, v=y.

Thanku Anjan :).