Two cones are similar. The surface area of the larger cone is 65 pi square inches. The surface area of the smaller cone is 41 point 6 pi square inches. The radius of the smaller cone is 6 point 4 inches. What is the radius of the larger cone?

For similar cones, surface areas scale as the square of the ratio of corresponding lengths. The area ratio is 65π ÷ 41.6π = 1.5625, so the radius scale factor is √1.5625 = 1.25. The larger radius is 6.4 × 1.25 = 8 inches, so the correct choice is A, 8 inches.

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