The circumference of a circle is given by the following formula
[tex]C=2\pi r[/tex]where r represents the radius.
The ratio between two circumferences is equal to the ratio of the radius.
[tex]\frac{C_1}{C_2}=\frac{2\pi r_1}{2\pi r_2}=\frac{r_1}{r_2}[/tex]The area of a circle is given by the following formula
[tex]A=\pi r^2[/tex]Then, the ratio between two circle areas is equal to the square of the ratio of the radius, which is the square of the ratio between the circumferences.
[tex]\frac{A_1}{A_2}=\frac{\pi r_1^2}{\pi r_2^2}=(\frac{r_1}{r_2})^2=(\frac{C_1}{C_2})^2[/tex]Then, applying this relation in our problem, the ratio between the areas is:
[tex]\frac{A_1}{A_2}=(\frac{30}{12})^2=\frac{25}{4}[/tex]The ratio between the areas is 25/4.
