Answer:
7) 28.27 cm²
8) 63.62 ft²
9) 113.10 in²
Explanation:
You want the areas of the circles with the given diameters.
Area
The area formula for a circle is usually written in terms of the radius of the circle. Since the diameter is given, we can rewrite the formula to make use of the diameter:
A = πr²
A = π(d/2)² . . . . . . . use d/2 for r
A = (π/4)d² . . . . . . . collect constants
Application
7) Diameter = 6 cm; Area = (π/4)(6 cm)² = 9π cm² ≈ 28.27 cm²
8) Diameter = 9 ft; Area = (π/4)(9 ft)² = 20.25π ft² ≈ 63.62 ft²
9) Diameter = 12 in; Area = (π/4)(12 in)² = 36π in² ≈ 113.10 in²
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