Question

the slant height of a frustum of a cone is 4 cm and the perimeter is its circular ends are 18 cm and 6 cm find the CSC of the frustum ​

Answer 1

Answer:

perimeter =2×22/7×r1

18=2×22/7×r1

r1=18/2×7/22

similarly

r2=6/2×7/22

csa=22/7×l(r1+r2)

Answer 2

Given,

Slant height of frustum of cone (l) = 4 cm

Let ratio of the top and bottom circles be r1 and r2

And given perimeters of 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 of frustum of a cone = π(r1 + r2)l

= (πr1+πr2)l = (9 + 3) × 4

 = (12) × 4 = 48 cm2

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