Question

The total surface area of frustum cone is 1,500 $f{t}^2$. The radius of a top cone is 10 and the bottom cone is 12 ft. What is the curved surface area of a frustum cone? (Use $\pi$ = 3).

• A. $789$ $f{t}^2$
• B. $765$ $f{t}^2$
• C. $790$ $f{t}^2$
• D. $768$ $f{t}^2$

Answer 1

Answer: (D)

$768$ $f{t}^2$

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

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

Therefore, $1,500$ $=$ Curved surface area $+\pi ({12}^2+{10}^2)$

$1,500$ $=$ Curved surface area $+(143\times 4+100)$

$1,500-732$ $=$ Curved surface area

Curved surface area $=$ $768$ $f{t}^2$