3. 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 or equation for the exact area of the sidewalk. (b) find the approximate area of the sidewalk. use 3.14 to approximate π.

121pi - 81pi or 125.6 square meters

To find this answer, imagine that you have one circle inside of another.  The area between the two circles forms a ring around the outside. To find this area, subtract the larger circle from the smaller circle.

Since the area of a circle is pi x r ^2, the area is:
pi x 11^2 minus pi x 9^2
Or
121 pi minus 81 pi

If you sub in 3.14, you will get an approximate area of 125.6.