## Elementary Geometry for College Students (6th Edition)

r $\approx$ 6.7cm
Given A metal circular disk whose area is 143 $cm^{2}$ is used as a knockout on an electrical service in a factory The area A of a circle whose radius has length r is given by A = $\pi r^{2}$ 143 = $\pi r^{2}$ $r^{2}$ = $\frac{143 * 7}{22}$ = 45.5 r = $\sqrt 45.5$ r = 6.746 cm r $\approx$ 6.7cm