If we assume that the distance travelled after they cross each other is the same, then we can set up a ratio. We know that

`v=d/t` for both trains

and that can be rearranged to

d = v*t

If the distance is the same for both trains

d(A) = d(B)

then the following must also be true

v(A)*t(A) = v(B)*t(B)

Where v and t are the velocity and time of each train (designated by A or B).

We can then rearrange that to find

`(v(A))/(v(B)) = (t(B))/(t(A))`

Since we know that the time for train A is hour and for train B is 2 hours (assuming that because of the way they are written in the problem), then we know that

`(v(A))/(v(B))=2/1`

So Train A is travelling twice as fast as Train B.

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