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(in cm2).
Slant height of a frustum of a cone = l =4 cm
Perimeter of its first circular end =18 cm
Perimeter of its second circular end =6 cm
Curved Surface Area of frustum of the cone = π.(r1+r2)l
= (π.r1+π.r2)l=(2π.r1+2π.r2)l2=(18+6)4/2=48cm2