Question

Find the volume and surface area of a cone with diameter 8 cm and height 8 cm.

Answer 1

Volume = $\frac{1}{3}$ $\pi r^{2}h$

= $\frac{1}{3}$ $\pi \left(4{)}^2\right(8)$

= 134.04 $c{m}^3$

Remember if diameter = 8 cm, we use radius = 4cm

Surface Area = area of base circle + area curved surface

= $\pi r^2+\pi r$ ( slant height)

Now we need to use Pythagoras to get the slant heights:

So now

$s^2=8^2+4^2$

$s^2=80$

$s=\sqrt{80}$

SA = $\pi (4{)}^2+\pi (4\left)\right(\sqrt{80})$

= 162.66 $c{m}^2$