Question

If the height and slant height of a cone are $21cm$ and $28cm$ respectively. Find its volume.

Answer 1

Height of a cone $\left(h\right)=21cm$

And slant height $\left(l\right)=28cm$

$\therefore$ Radius $=\sqrt{l^2-h^2}$

$r=\sqrt{{28}^2-{21}^2}$

$=\sqrt{784-441}$

$=\sqrt{343}cm$

$=7\sqrt{7}cm$

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

$=\frac{1}{3}\times \frac{22}{7}\times (7\sqrt{7}{)}^2\times 21$

$=22\times 343$

$=7546c{m}^3$