13)
Circumference (C) = 2π·r
11π = 2π·r
11/2 = r
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Area (A) = π·r²
= π·(11/2)²
= 121π/4
≈ 94.985 in²
14)
diameter = 2r
42 = 2r
21 = r
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Area (A) = π·r²
= π·(21)²
= 441π
≈ 1384.74 in²
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$280/1384.74 in²
x = $0.20
Answer: about 20 cents per square inch