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Question
The radii of the ends of a frustum are 14 cm and 6 cm respectively and its height is 6 cm. Find its curved surface area.
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Solution
Given: Radii (r1) = 14 cm, r2 = 6 cm, height (h) = 6 cm
Slant height of the frustum (l)
= `sqrt(h^2 + (r_1 - r_2)^2)`
= `sqrt(6^2 + (14 - 6)^2)`
= `sqrt(6^2 + 8^2)`
= `sqrt(36 + 64)`
= `sqrt(100)`
= 10 cm
Curved surface area of the frustum
= πl (r1 + r2)
= 3.14 × 10 (14 + 6)
= 3.14 × 10 × 20
= 628 cm2
∴ The curved surface area of the frustum is 628 cm2.
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