## Intermediate Algebra (12th Edition)

$(a)~r=240$ in $(b)~d=480$ in
We know that the circumference of a circle is given by the formula: $Circumference=2\pi~radius$ $C=2\pi r$ We can solve for the radius, $r$: $r=\frac{C}{2\pi}$ We plug in $C=480\pi$ in: $r=\frac{480\pi}{2\pi}$ $r=240$ in (b) We know that the diameter relates to the radius by the formula: $diameter=2*radius$ $d=2r$ We plug in $r=240$: $d=2*240=480$ in