plain and short, an hour has 60 minutes, and a minute has 60 seconds, therefore an hour has 60*60 or 3600 seconds, and we can express that rate as hr/3600s or the other way around 3600s/hr, depending on which version we need.
a mile has 5280 feet, again, we can use that rate as mile/5280ft or 5280ft/mile, as needed.
[tex]\bf \cfrac{300 ft}{2.29 s}\cdot \cfrac{3600 s}{hr}\cdot \cfrac{mi}{5280 ft}~\hspace{10em}\stackrel{\textit{using minutes as well}}{\cfrac{300 ft}{2.29 s}\cdot \cfrac{60 min}{hr}\cdot \cfrac{60 s}{min}\cdot \cfrac{mi}{5280 ft}}[/tex]
