keeping in mind that
there are 1.609 kms in 1 mile
5280 feet in 1 mile
and 60 minutes in 1 hr.
[tex]\bf \cfrac{9~\underline{km}}{\underline{hr}}\cdot \cfrac{\underline{mile}}{1.609~\underline{km}}\cdot \cfrac{5280~ft}{\underline{mile}}\cdot \cfrac{\underline{hr}}{60~mins}\implies \cfrac{9\cdot 5280~ft}{1.609\cdot 60~mins}
\\\\\\
\cfrac{47520~ft}{96.54~mins}\approx 492.2311995\frac{ft}{min}[/tex]