Chapter 10 - Area - 10-7 Areas of Circles and Sectors - Practice and Problem-Solving Exercises - Page 663: 12

$25 \ \pi \approx 78.5 \ mi^2$

Let $A$ be the area of a circle. The area $(A)$ of a circle whose radius is $R$ is given by: $A=\pi r^2 ...(1)$ We are given that radius $r=5 \ mi$ Plug the data in the equation (1) to obtain: $A=\pi (5)^2=\pi(25)$ Therefore, we get , $Area=25 \ \pi \approx 78.5 \ mi^2$