Aptitude - Problems on Trains - Discussion

Why we are taking 2x?

Hello Friends,
If 2 trains of length a and b moving in same direction at u,v.Then the time taken by the faster train to cross the slower train is =(a+b)/(u-v)sec.
So here,Time=36sec and u+v=25/9m/sec
Then the formula is,36=(a+b)/(925/9)
a+b=100
Now we get a=50 and b=50
I think ur doubt is clear now

The correct answer is 100 mts. We can take the length of only one train as answer as both the trains started at the same point and time. The faster train has just to cover its length only to cross the slower train. The formula is:

((46-36)kmph*5/18)*36=50/18*36=100mts.

------------- Added by Author -----------------------------------
This answer is wrong. We have to read the question very carefully, there is no information like "started at the same time and same point".
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We can slove like this
relative speed =10km/hr
distance=speed*time
=(10*5/18)*36
=100m
distance=sum of length of train
since both r equal length
length of each =50m

Hi jayanth
read the problem carefully its given that the trains of equal length

How can we take 2X there?

How can we take 2X there?

It's simple

We know the formula
u=(a+b)/x-y
let us take the lengh of the train is z(both trains len are same)
then
36=(z+z)/(46-36)*5/18
z=50m

How it is possible? train length = x metres then distance =2x metres.

I think we can do like:

Relative speed is (46-36);

Length = (10*5/18)*36;
=100both
=50 each.