Question

Find the total surface area of the cone, if its slant height is $21m$ and diameter of its base is $24m$,[Assume $\pi =\frac{22}{7}$]

Answer 1

Given,

Slant height of cone is $l=21m.$

Diameter of its base is $d=24m.$

hence, radius of its base is $r=\frac{d}{2}=12m.$

Now, the total surface area of cone is given by

$S=\pi rl+\pi r^2$

$S=\pi (rl+r^2)$

$S=\pi (12\times 21+{12}^2)$

$S=\pi (252+144)$

$S=\frac{22}{7}\times 396$

hence, $S=1244.57m^2$