Question

Pls hrlp.................no.8

Answer 1

The area of a cone comprises lateral and base surface area.

The height of the cone is 12 m and radius of the base is 16 m.

The area is gotten by the formula. (Please look at the bottom.)

$l=\sqrt{12^2+16^2} =20$

$\pi\times 16\times (16+20)=576\pi$

The surface area of the cone is  $576\pi$m².

The area of the cloth is  $576\pi$m².

The cloth is a rectangle.

The length required is $\frac{576}{1.1}\pi =\frac{5760}{11} \pi$.

Cost : ₹ $\frac{161280}{11} \pi$

formula

Let the height be $h$, base radius $r$.

Then, by the pythagorean theorem,

the radius of the lateral surface is $\sqrt{r^2+h^2}$.

Let $l=\sqrt{r^2+h^2}$.

(lateral surface area) = $\pi \times l^2 \times \frac{2\pi \times r}{2\pi \times l} =\pi rl$

(Because lateral surface is a circular sector, not a full circle.)

(base area) = $\pi r^2$

∴ (surface area of a cone) = $\pi r^2+\pi rl=\pi r(r+l)$