Question

Find the area of copper sheet required to make a bucket of height 8 cm and radii 9 cm and 3 cm.

• A. $109c{m}^2$
• B. $129c{m}^2$
• C. $129\pi c{m}^2$
• D. $105c{m}^2$

Answer 1

The correct option is C $129\pi c{m}^2$

As bucket is in the form of frustum of cone. The area of the copper sheet required to make the bucket is curved surface area plus bottom surface area of frustum.

$=\pi (r_1+r_2)l+\pi r_2^2$, where $l$ is the slant height of the frustum.

$\Rightarrow$ area of the copper sheet
$=\pi (9+3)\times \sqrt{{(9-3)}^2+8^2}+\pi \times 3^2$ $[\because l\sqrt{{(r_1-r_2)}^2+h^2}]$
$=129\pi c{m}^2$