## Algebra: A Combined Approach (4th Edition)

$r=2.5$
$C=2\pi r;$ $C=15.7$ Substitute known values. (Let $\pi=3.14$) $15.7=2(3.14)r$ Solve for $r$ by dividing both sides of the equation by $2(3.14)$: $\dfrac{15.7}{2(3.14)}=\dfrac{2(3.14)r}{2(3.14)}$ $r=\dfrac{15.7}{2(3.14)}=2.5$