Question

The lateral surface area of a right circular cone of height 28 cm and base radius 21 cm is:

• A. 1155 $c{m}^2$
• B. 1055 $c{m}^2$
• C. 2110 $c{m}^2$
• D. 2310 $c{m}^2$

Answer 1

The correct option is D

2310 $c{m}^2$

Given, h = 28 cm; r = 21 cm

Therefore, slant height (l) = $\sqrt{{28}^2+{21}^2}$

= 35 cm

Lateral surface area = $\pi$rl

= $\frac{22}{7}$ × 21 × 35

= 2310 $c{m}^2$