Aptitude - Problems on Trains - Discussion

Length of the trains be x & 2x because after 36 second the faster train is going to pass the slower train. At that time faster train covers 460m and slower train covers 360m. The difference is 100m. This difference is between faster train's front edge and slower train's back edge.

Then it involves the distance of both the trains, hence we need to divide 100m by 2 (because in the question they've given as both the trains of equal length) to get the length of the train.

If a train has the length x and the other train of same length cross the train of length than distance travel by it must be x so my query is why we are taking length 2x instead of x. Please tell.

It should be mentioned that the faster train started behind the slower train.

If both trains are started at same place then we do not get 2x, because faster train only cover x area which is his own length.

Should be mentioned that the faster train started behind the slower train.

What is relative speed?

In the question it's clearly mentioned two trains are of same length.

So we can use formula , two trains or two objects bodies are moving in the same direction at u m/s and v m/s, where u > v, then their relative speed is = (u - v) m/s.

* So 46-36=10km/hr.
* 10 *5/18 : 25/9
* 25/9*36 :.100 ( both train )
* 100/2=50 each train.

Thanks.

Use formula
L=length S=Speed
(L1+L2)/(S1-S2)=Time taken by fast train to cross slow train

Let length of train be x
Relative speed = (46-36) * 5/18 m/s =50/18
(x+x)/(50/18) = 36
2x/50=2
2x=100
x=50.

If both are of same length but time taken by A to cross B is given i.e 36 minutes, it does not mean that the B train is at Rest.

B is also moving so total distance cover by A = length of A + length of B + some distance after starting.

Total dist travel by B = 360 m
Total dist travel by A = 460 m
Therefore diff is 100 m

i.e. Length of train A or B

In the question clearly mentioned two trains are same length.

So 46 - 36 : 10
10 *5/18 : 25/9
25/9*36 :.100

So both are 100 meters.
So each train 50 meters.

Whether the trains are in same or in opposite directions we are to add the lengths of trains for covering distances you can check it.

The answer is correct.