Question

The ratio of slant height and radius of a cone is $7:4$. If its curved surface area is $792{cm}^2$, then find its radius.

• A. $12cm$
• B. $21cm$
• C. $28cm$
• D. $33cm$

Answer 1

Answer: (A)

$12cm$

Let the slant height be $7x$ and radius be $4x$.

The curved surface area is given as $792c{m}^2$

$\pi rl=792$

$\frac{22}{7}\times 4x\times 7x=792$

$x^2=\frac{792}{22\times 4}$

$x^2=9$

$x=3$

The radius is,

$r=4\times 3$

$=12cm$