The formula for the circumference is: [tex]2\pi r[/tex] So to find first radius: [tex]2\pi r = 12\pi \\ \\ \pi r = 6\pi \\ \\ r = 6[/tex] Second radius: [tex]2\pi r = 18\pi \\ \\ \pi r = 9\pi \\ \\ r = 9[/tex] The ratio between them is: [tex] \frac{6}{9} = \frac{2}{3} = 0.66667[/tex]
