If ship B is traveling due east at a speed of , then the total distance traveled after hours is km. However, Ship A leaves a half hour before, traveling at a speed of . The distance traveled by Ship A would have to be km, since Ship A has been traveling a half hour longer that Ship B. When drawn, these two distances can be represented as legs of a triangle, with the hypotenuse being the distance between the ships. Thus, using the Pythagorean Theorem, we find that distance to be:

Plug in 2 for t to find how far apart they are.

Hope my explanation was clear!