the radius of a circle is 9 feet. what is the diameter? give the exact answer in simplest form.

The diameter of a circle equals twice the radius of that circle.
Then:
[tex]\begin{gathered} D=2\times r \\ =2\times9ft \\ =18ft \end{gathered}[/tex]Therefore, the diameter of the circle is:
[tex]18\text{ feet}[/tex]