[tex]A=\pi r^2= \frac{\pi d^2}{4} [/tex]
(at diameter = 2): [tex] \frac{\pi\times2^2}{4} = \pi [/tex]
(at diameter = 5): [tex] \frac{\pi \times 5^2}{4} = \frac{25}{4} \pi[/tex]
ratio = [tex]\pi[/tex]:[tex] \frac{25}{4} \pi[/tex] = [tex]1: \frac{25}{4} [/tex] = [tex]4:25[/tex]
