Question

Both circles have the same center. The circumference of the inner circle is 150.72 feet. What

is the area of the shaded region?

Answer 1

Explanation:

The circumference = 2 * pi * r = 150.72

Use this fact to find r

2*pi*r = 150.72 Divide by pi

2*r = 150.72 / 3.141

2*r = 47.985 Divide by 2

r = 23.9923

Now that you have the radius of the inner circle, use it to find the area.

Area = pi * r^2

Area = 1808.064

Now we need the radius of the outer circle

r = 23.9923 + 11

r = 34.9923

Find the area of the other circle

Area = pi * 34.9923^2

Area = 3846.032

Finally the area of the shaded region is the area of the large circle - the area of the small circle

Area of the shaded area = 3846.032 - 1808.064

Area of the shaded area = 2037.97 to the nearest hundredth.