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To find the surface area of a cone, we need to add the area of the base (Ï€r^2) and the lateral surface area (Ï€rl).
Given:
r = 9
l = 21
Base area = π(9)^2 = 81π
Lateral surface area = π(9)(21) = 189π
Total surface area = Base area + Lateral surface area
Total surface area = 81Ï€ + 189Ï€ = 270Ï€
To find the surface area to the nearest tenth, we need to calculate the value of 270Ï€.
Using 3.14159 as the value of π:
270 * 3.14159 = 848.2303
Therefore, the surface area of the cone to the nearest tenth is 848.2 cm².