The radii of the circular ends of a solid frustum of a cone are 18 cm and 12 cm and its height is 8 cm. Find its total surface area. [Use π = 3.14.]
Given: Radius of lower circular end = r = 12 cm
Radius of upper circular end = R = 18 cm
Height of frustum = h = 8 cm
Formula: Total surface area of frustum = πr2 + πR2 + π(R + r)l cm2
Where l = slant height
For slant height we have
∴ l = 10 cm
∴ total surface area of frustum = π × 122 + π × 182 + π × (18 + 12) × 10 cm2
= 3.14 × (144 + 324 + 300) cm2
= 3.14 × 768 cm2
= 2411.52 cm2
∴ total surface area of frustum = 2411.52 cm2
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