Question

The slant height of a frustum of a cone is 15 cm, the upper and lower radii are 12 cm and 8 cm respectively. The curved surface area of the frustum of cone is

• A. $314\pi c{m}^2$
• B. $300\pi c{m}^2$
• C. $280\pi c{m}^2$
• D. $408\pi c{m}^2$

Answer 1

The correct option is B $300\pi c{m}^2$

Slant height of a frustum of cone, l = 15 cm

Upper radius, R = 12 cm


Lower radius, r = 8 cm

Curved surface area of frustum of cone = π(R + r)l
= π × (12 + 8) × 15
$=300\pi c{m}^2$

Hence, the correct answer is option (b).