The circumference of the base of a cone is 24 pi inches. The slant height of the cone is 20 inches. What is the surface area of the cone? Express the answer in terms of pi

Use the circumference, 2πr = 24π, to find the radius: r = 12 inches. The cone’s total surface area is the lateral area plus the base area: πrl + πr² = π(12)(20) + π(12²) = 240π + 144π = 384π square inches. Therefore, the correct choice is D, 384π square inches.

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