Aptitude - Problems on Trains - Discussion

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:.

Its given as Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds.

So it should be taken as 27x and 17x seconds only, I don't know why it is given as 27x and 17y meters and also denoted as length of train. Please any one explain me?

@k.kiran kumar
27x+17y/x+y
here as the two trains cross each other total distance they travelled is length of them.As given in problem they cross in 23 seconds.
time=distance/speed
i.e 23=27x+17y/x+y

Fast calculation = mod(23-17) : mod(23-27) = 6:4 = 3:2 .

I agreee with Rohit calculation.

Can anyone tell me the formulas for relative speed ?

27x+17y total distance.

X+y=total speed.

Total distance/total speed=total time.

Total time= 23 given.

Solve it.

Distance=speed*time.
1st train time =27sec. 2nd train time =17sec.
two trains can cross the each other in opposite direction is 23 sec.
so total time=(total distance)/totalspeed;
total distance,
1st&2nd train have speed x,y;
total distance=27x+17y; total speed=x+y;
23=(27x+17y)/x+y;
23x+23y=27x+17y;
6y=4x;
6/4=x/y;
3/2=x/y;
3:2

Can any one tell me how to calculate mod(23-17) : mod(23-27)

I forgot how to calculate mod and if we are calculating same mod(23-17) : mod(23-27) then how it comes to 6:4????

First you have to know that mod(positive or negative value) = positive value

So mod(23-17)=6
mod(23-27)=mod(-4)=4

Hope you understood.

Really it is helpful to get qualify related aptitude exam I thank from my side to indiabix. Com and easy to understand solution also.