We use the unit multiplier 



So that the ft on top will cancel with the ft on the bottom.

Next use the unit multiplier 



So that the min on the bottom will cancel with the min on the top.

Now we cancel the "ft":



also we cancel the "min":



And we get:


or

or



When you get skilled in this type of problem, you'll be
able to do it in your head like this:

15 feet is 3 yards, so that's 5 yards in one minute. Then in 1 hour
it goes 60 times as far, and 60 times 5 is 300.  So it goes 300 yards
in 1 hour.  

Edwin