Question

At the mission museum Mrs. Perez visited over break, there is a pond like the one below that has a ring shaped sidewalk around it. The outer edge of the sidewalk is a circle with a radius of 10 m. The inner edge of
the sidewalk is a circle with a radius of 8 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 .

Answer 1

The formula for area of a circle is : A = PI x r^2

A) find the are of the two circles, subtract the two to find the area of the side walk:

Outside circle: A = PI x 10^2

Area = 100PI

Inner circle: A = PI x 8^2

Area = 64PI

Area of sidewalk:

100PI - 64 PI = 36PI

B) replace PI with 3.14:

Area = 36 x 3.14 = 113.04 square meters.