Question

An ice cream cone has base radius 6 cm and altitude 8 cm. The total surface area of 21 such cones is

• A. 6336 cm²
• B. 5226 cm²
• C. 4356 cm²
• D. 5280 cm²

Answer 1

The correct option is A

6336 cm²

Given, radius (r) = 6 cm, height (h)=8 cm.
Let slant height = l
We know that, $l^2=r^2+h^2\Rightarrow l=\sqrt{r^2+h^2}\Rightarrow l=\sqrt{6^2+8^2}=\sqrt{100}=10cm$
Total surface area of one cone
$=\pi r(l+r)=\frac{22}{7}\times 6\times (10+6)=\frac{2112}{7}c{m}^2$

Now, total surface area of 21 such cones = $21\times \frac{2112}{7}=6336c{m}^2$