Question

At a zoo, the lion pen has a ring-shaped sidewalk around it. The outer edge of the sidewalk is a circle with a radius of 11 m. The inner edge of the sidewalk is a circle with a radius of 9 m. (a) Write and simplify an expression for the exact area of the sidewalk. (b) Find the approximate area of the sidewalk. Use 3.14 to approximate π.

Answer 1

The formula for finding area of a circle is $\pi r^2$ . 

Essentially, we have two circles here. One is a larger outer circle, and the other in a smaller inner circle. In order to find the area of the sidewalk, we must find the area of the outer circle, then find the are of the inner circle. After we find both areas, we subtract. 

See attached image for process of finding area, and subtracting areas to find the final area of the sidewalk.