Question

The radius and the slant height of a cone are in the ratio 4 : 7. If its curved surface area is 792 $c{m}^2$, find its radius $(use\pi =\frac{22}{7})$ [3 MARKS]

Answer 1

Formula: 1 Mark
Application: 1 Mark
Solution: 1 Mark

Given $r:l=4:7$
If r= 4x, then l = 7x
Curved surface area of cone = $792c{m}^2$
$\Rightarrow \pi rl=792\Rightarrow \frac{22}{7}\times 4x\times 7x=792\Rightarrow x^2=\frac{792}{88}=9\Rightarrow x=3cm$
$\therefore$ Radius of cone, $r=4x=4\times 3=12cm$