Answer
$\frac{1}{2}$ ft
Work Step by Step
We know that the length of the arc $s$ cut off by $\theta$ can be calculated as $s=r\theta$. Therefore, we also know that $r=\frac{s}{\theta}$.
We are given that $\theta=6$ and $s=3$ ft.
Therefore, $r=\frac{3}{6}=\frac{3\div3}{6\div3}=\frac{1}{2}$ ft.