Question

Find the curved surface area of a frustum of cone. The slant height is 20 cm, top and bottom radius is 11 and 15 cm respectively. (Use $\pi$ = 3)

• A. 1,860 cm${}^2$
• B. 1,760 cm${}^2$
• C. 1,660 cm${}^2$
• D. 1,560 cm${}^2$

Answer 1

The correct option is D 1,560 cm${}^2$

Curved surface area $=\pi \times l\times (R+r)$

$=3\times 20\times (11+15)$

$=3\times 20\times \left(26\right)$

$=3\times 520$

$=1,560c{m}^2$