Question

The curved surface area of a cone is 670 cm${}^2$ and its radius is 15cm Find its slant height and total surface area

• A. 13770.4 cm${}^2$
• B. 1377.04 cm${}^2$
• C. 137.704 cm${}^2$
• D. 137704 cm${}^2$

Answer 1

The correct option is B 1377.04 cm${}^2$

Curved surface area of the cone = $\pi rl=670c{m}^2$
or $\frac{22}{7}\times 15\times 1=670orl=\frac{670\times 7}{22\times 15}=14.21cm$
$\therefore$ Total surface area = $\pi r(r+l)\frac{22}{7}\times 15(15+14.21)=1377.04c{m}^2$