Question

the radius of the inner white circle of the doughnut is 2cm. The circumference of the outer edge of the doughnut is 43.96cm. What is the area of just the brown part of the doughnut (excluding the inner white section)?

Answer 1

141.4 sq cm

Explanation:

to find the area of the outer circle with a smaller circle inscribed within, you find the area of each and subtract the smaller area from the larger

the radius of the smaller circle is 2

we have to find the radius of the larger circle so we use what we know about its circumference:

C = 2πr

43.96 = 2πr

21.98 = πr

21.98 / π = r

r ≈ 7 cm

now use r = 7 to find area of larger circle:

A = πr²

A = π49

Area of smaller circle: 4π

Area of larger circle without including inner section is 49π - 4π = 45π

45π ≈ 141.4 sq cm