surface area of formula = \pir\(^2\) If the radius is reduced then let its radius be x. Its area is \pix\(^2\) . x : r = 2 : 5, so \(\frac{x}{r}\) = \(\frac{2}{5}\) → 5x = 2r Hence, x = 0.4r. Hence the area of the new circle is \pi (0.4r)\(^2\) = 0.16\pi r\(^2\) . The ratio of the two areas is 0.16\pir\(^2\) : \pir\(^2\) = 0.16 : 1 = 16 : 100 = 4 : 25.