Question

the slant height of the frustrum of a cone is 4cm and the perimeter of its circular base are 18cm and 6cm respectively. Find the curved surface ares of the frustrum

Answer 1

Hello dear,

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Perimeter of upper circular end of frustum = 18 cm

2πr1 =18

$r1 = \frac{9}{\pi}$


Perimeter of lower end of frustum = 6 cm

2πr2 = 6

$r2 = \frac{3}{\pi}$


Slant height (l) of frustum = 4 cm

CSA of frustum = π (r1 + r2) l

$= \pi( \frac{9}{\pi} + \frac{3}{\pi} )4 \\ = 12 \times 4 \\ = 48 \: {cm}^{2}$


Therefore, the curved surface area of the frustum is 48 cm2.

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