Question -
Answer -
Given,
Slant height offrustum of cone (l) = 4 cm
Let ratio of the topand bottom circles be r1 and r2
And given perimetersof its circular ends as 18 cm and 6 cm
⟹ 2πr1 =18 cm; 2πr2 = 6 cm
⟹ πr1=9 cm and πr2 = 3 cm
We know that,
Curved surface area offrustum of a cone = π(r1 + r2)l
= π(r1 +r2)l
= (πr1+πr2)l =(9 + 3) × 4 = (12) × 4 = 48 cm2
Therefore, the curvedsurface area of the frustum = 48 cm2