Question

The total surface area of frustum cone is 450 $m^2$. The diameter of a top cone is 2 and the bottom cone is 5 m. What is the curved surface area of a frustum cone? (Use $\pi$ = 3).

• A. 410.25 $m^2$
• B. 428.25 $m^2$
• C. 420.32 $c{m}^2$
• D. 430.02 $m^3$

Answer 1

The correct option is B 428.25 $m^2$

Total surface area = $\pi (R+r)s+\pi R^2+\pi r^2$

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

Diameter = radius $\times 2$

Radius, R = 2.5 m, r = 1 m

Therefore, 450 = Curved surface area $+\pi ({2.5}^2+1^2)$

450 = Curved surface area $+3\times (6.25+1)$

$450-21.75=$Curved surface area

Curved surface area = 428.25 $m^2$