Answer:
477.52 square inches
Explanation:
The outside diameter is (3 1/2 ft)(12 in/ft) = 42 inches. So, its radius is 21 inches.
The inside diameter is 2 ft 10 in = 34 inches. So, its radius is 17 inches.
The difference in areas of a circle with 21 inch radius and a circle with 17 inch radius will be found using the area formula for a circle:
A = πr²
The area difference is ...
rim area = π((21 in)² -(17 in)²) = 152π in²
rim area ≈ 477.52 in²
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Comment on the calculation
To have an answer accurate to 5 significant digits, you must use a value for pi that is accurate to at least 5 significant digits: 3.1416 or 3.14159.