## Elementary Geometry for College Students (7th Edition)

The radii of two concentric circle differ in length by exactly 1 in. The area differ by exactly 7$\pi$ $in^{2}$ Let us assume the outer circle radius R and inner circle radius r From the given condition R-r = 1 ..................... eq1 A1 - A2 = $\pi (R^{2} - r^{2})$ 7$\pi$ = $\pi$ (R+r)(R-r) 7 = R+r .............................................eq2 Solve eq1 and eq2 R-r = 1 R+r = 7 2R = 8 R = 4 in R-r = 1 4 -r = 1 r = 4-1 = 3in The outer circle radius R = 4 in The inner circle radius r =3 in