Question

Slain height of frustum of cone is 9 cm and perimeter of its circular base is 18 cm and 16 cm respectively what is the curved surface area of the frustum

Answer 1

SOLUTION:-

Given:

•Slant height of frastum of cone is 9cm & perimeter pf it's circular base is 18cm & 16cm respectively.

To find:

The curved surface area of the frastum.

Explanation:

Formula

The curved surface area of the frastum cone;

=) π(r1 + r2)l

•Slant height,(l)= 9cm.

Therefore,

In first Case r1;

Circumference of the circle= 2πr1

$= > 2 \times \frac{22}{7} \times r1 = 18 \\ \\ = > \frac{44}{7} \times r1 = 18 \\ \\ = > r1 = \frac{18 \times 7}{44} \\ \\ = > r1 = 2.86cm$

In Second case r2;

Circumference of the circle= 2πr= 16

$= > 2 \times \frac{22}{7} \times r2 = 16 \\ \\ = > \frac{44}{7} \times r2 = 16 \\ \\ = > r2 = \frac{16 \times 7}{44} \\ \\ = > r2 = 2.54cm$

Now,

CSA of the frastum:

$= > \pi(r1 + r2)l \\ \\ = > \pi(2.86 + 2.54) \times 9 \\ \\ = > \pi(5.4) \times 9 \\ \\ = > \frac{22}{7} \times 5.4 \times 9 \\ \\ = > \frac{1069.2}{7} {cm}^{2} \\ \\ = > 152.74 {cm}^{2}$

Thus,

The curved surface area of frastum is 152.74cm².

Thank you.