Question

Find the total surface area of a cone, if its slant height is $21m$ and distance of its has is $24m$.

Answer 1

We have,

Slant height$=21m.$

Distance$=24m.$

We know that,

$Distance=Circumference$

Circumference$=2\pi r=24$

$\pi r=12$

$r=\frac{12}{\pi }$

$r=\frac{12}{\frac{22}{7}}$

$r=\frac{12\times 7}{22}$

$r=\frac{84}{22}$

$r=\frac{42}{11}$

$r=3.819m.$

Now,

Total surface are of cone$=\pi rl$

So,

$=\frac{22}{7}\times 3.819\times 21$

$=22\times 3.819\times 3$

$=66\times 3.819$

$=252.054m^2$

Hence, this is the answer.