Question

The total surface area of frustum cone is 360 $f{t}^2$. The radius of a top cone is 6 and the bottom cone is 4 ft. What is the curved surface area of a frustum cone? (Use $\pi$ = 3.14).

• A. 116.72 ft
• B. 126.72 ft
• C. 106.72 ft
• D. 146.72 ft

Answer 1

The correct option is C 106.72 ft

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

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

Therefore, 360 = Curved surface area $+\pi (6^2+4^2)$

270 = Curved surface area $+3.14(36+16)$

$270-163.28=$Curved surface area

Curved surface area$=106.72ft$