Answer:
40π/3 cm^2 ≈ 41.89 cm^2
Step-by-step explanation:
The centerline of the shaded region has a radius of 3cm+(4 cm)/2 = 5 cm. Its length is 1/3 that of the circumference of a circle with that radius (because 120° is 1/3 of 360°).
The area is the product of the centerline length and the width of the shaded area (4 cm).
shaded area = (1/3)(2π(5 cm))(4 cm)
shaded area = 40π/3 cm^2 ≈ 41.89 cm^2
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<em>Alternate solution</em>
The area of the donut is the difference in the areas of the outer and inner circles:
πr₂² -πr₁² = π((7 cm)^2 -(3 cm)^2) = 40π cm^2
The are of the shaded region is (120°/360°) = 1/3 of that, so is
shaded area = (40/3)π cm^2
