Aptitude - Problems on Trains - Discussion

The distance covered is (X+X) = 2X.

Let, the speed of 1st&2nd train as x & y.

So, Apply the formula,

5/18(x-y)*T (T as time) = 5/18(46-36)*36.

= 50*36/18.

= 100.

So, we have 2X = 100.

X = 100/2 = 50 m.

When the two trains start running with different speed, the speeder train will get ahead of the slower train at some time.

With both the train running, it is hard to find the distance after which the speeder train completely pass the slower train.

To make it easy, find the relative speed of the train. It is 4km/hr. It can be said that when the slower train speed is 0km/hr, the speeder train speed is 4 km/hr.

Assume the slower train stops or consider it as a platform, then the speeder train cross the slower train in 36 seconds @ 4km/hr. Here the total distance covered is length of speeder train and the platform (slower train)

Have a good day.

Hello friends,

Can anyone please explain me how the distance covered it 2X he has not provided any information that first train is behind the other train?

Relative speed = 45-35 = 10.

= 10* (5/18) = 25/9.

Distance = (25/9) *36.

= 25*4.

= 100 FOR BOTH TRAINS.

SO = 50 FOR EACH TRAIN.

I think we can do it in a different way.

Distance = Speed*Time.

= (46-36) *5/18*36.

= 100.

This is the length of two trains.

And it is given that length of both the trains are equal.

Therefore length of one train is equal to 50.

Please some one suggest that it is correct or not.

I didn't understand that why we are considering speed of slower train even its mention that faster crosses the slower one.

Why did you take 36 again two times please explain?

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.