Question

What is the total surface area of a right circular cone of height 14 cm, and base radius 7 cm? Consider $\sqrt{5}$= 2.236 and $\pi$ = 22/7.

• A. 344.35 cm²
• B. 462 cm²
• C. 498.35 cm²
• D. 154 cm²
• E. None of these

Answer 1

The correct option is C

498.35 cm²

h = 14 cm, r = 7 cm. So, l = $\sqrt{{\left(7\right)}^2+{\left(14\right)}^2}=\sqrt{245}=7\sqrt{5}cm$

$\therefore$Curved surface area = $\pi$rl + $\pi$r${}^2$ = $\left(\frac{22}{7}\times 7\times 7\sqrt{5}+\frac{22}{7}\times 7\times 7\right)$ cm${}^2$

= 154($\sqrt{5}+1\left)\right]$cm${}^2$= (154$\times$3.236) cm${}^2$ = 498.35 cm${}^2$