Question:
The radius and the height of a right circular cone are in the ratio 5:12. If its volume is 314 cubic meter, find the slant height and the radius. (Use π = 3.14).
Solution:
Let us assume the ratio to be y
Radius (r) = 5y
Height (h) = 12y
We know that
$1^{2}=r^{2}+h^{2}$
$=5 y^{2}+12 y^{2}$
$=25 y^{2}+144 y^{2}$
$=169^{2}=13 y$
Now it is given that volume $=314 \mathrm{~m}^{3}$
$\Rightarrow 1 / 3 \pi r^{2} h=314 m^{3}$
$\Rightarrow 1 / 3 * 3.14 * 25 y^{2} * 12 y=314 m^{3}$
$\Rightarrow y^{3}=1$
⟹ y = 1
Therefore,
Slant height (l) = 13y = 13 m
Radius = 5y = 5 m