Question 2 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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Solution
Slant height l = 4 cm, perimeters = 18 cm and 6 cm Radii can be calculated as follows: Radius=Perimeter2π Or,R=182π=9π andr=62π=3π Curved surface area of frustum =π(R+r)l =π(9π+3π)4 =48cm2