15. Five mark exercise problem VI

Two trains leave a railway station at the same time. The first train travels due west and the second train due north. The first train travels at a speed of $20 \ km/hr$ and the second train travels at $30 \ km/hr$. After $2$ hours, what is the distance between them?

 

The distance between the two trains is $i\overline{)i}$ $km$.