The circumference of a circle is given as:
[tex]C=\pi D[/tex]where D is the diameter. Plugging the value given and solving for D we have:
[tex]\begin{gathered} 138.16=(3.14)D \\ D=\frac{138.16}{3.14} \\ D=44 \end{gathered}[/tex]Now, the radius is twice the diameter, that means that:
[tex]r=\frac{D}{2}=\frac{44}{2}=22[/tex]Therefore the radius is 22 ft.