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Aaron creates a stacked cake comprised of three cylindrical sections as pictured below, and plans to cover the top of each section with a different color icing. Each lower section is a total of two inches wider than the section above it. If the yellow top of the upper section has an area of 12.56 square inches, what is the approximate area of the green visible portion of the bottom section which he will need to cover with icing?

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Answer:

Explanation:

A = πR²

top layer has a radius of

R = √(12.56/π) = 2 inches

The middle layer has a radius of 3 inches and an area of

A₂ = π3² = 9π in²

The bottom layer has a radius of 4 inches and an area of

A₃ = π4² = 16π in²

so the visible area on the bottom layer has an area of

16π - 9π = 7π in² or about 22 in²

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