Question

The slant height of a cone is 25 mm, top and bottom diameter is 0.2 and 0.4 mm respectively. Find the curved surface area of a frustum of cone. (Use $\pi$ = 3.14)

• A. 14.7 mm${}^2$
• B. 13.7 mm${}^2$
• C. 12.7 mm${}^2$
• D. 23.55 mm${}^2$

Answer 1

The correct option is D 23.55 mm${}^2$

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

Diameter = radius/2

Radius, R = 0.16 mm, r = 0.04 mm

$=3.14\times 25(0.16+0.04)$

$=3.14\times 25\left(0.2\right)$

$=3.14\times 5$

$=15.7m{m}^2$