Question

An ice cream cone has radius of $21$ m and height of $20$ m. Find total surface area of the cone.

• A. $3297m^2$
• B. $9734{cm}^2$
• C. $3297mm$
• D. $3297m$

Answer 1

The correct option is A $3297m^2$

Given, radius $r=21m$ and height $h=20m$.

Then, slant height is:
$s^2=h^2+r^2$
$⟹$ $s^2={20}^2+{21}^2$
$⟹$ $s^2=400+441$
$⟹$ $s=\sqrt{841}$
$⟹$ $s=29$ m.

Therefore, Total surface area of a cone $=\pi rs+\pi r^2$
$=3.14\times 21\times 29+3.14\times 21\times 21$
$=1912.26+1384.74$
$=3297m^2$.

Hence, option $A$ is correct.