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

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Perimeter of upper circular end of frustum = 18                 

 2πr1 =18                                                                             

r1 =9/π

Perimeter of lower end of frustum = 6 cm                            

2πr2 = 6                                                                             

r2= 3/π 

Slant height (l) of frustum = 4

CSA of frustum = π (r1 + r2) l

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

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