The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular endsare 18 cm and 6 cm. Find the curved surface area of the frustum


According to the question,

Perimeter of upper circular end of frustum = 18 cm


[2πr1 =18]


r1 =


Perimeter of lower end of frustum = 6 cm


2πr2 = 6


r2 =


Slant height (l) of frustum = 4 cm


CSA of frustum = π (r1 + r2) l


= π (+ ) * 4


= 12 * 4


= 48 cm2


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