Question

What is the radius and curved surface area of a cone made from a quadrant of a circle of radius $28cm$?

Answer 1

Length of arc$=l\theta =28\times \frac{\pi }{2}=14\pi$

Length of arc$=$circumference of base

$2\pi r={14}^2\pi$ so $r=7$cm

CSA of cone$=\pi rl$

$=\frac{22}{7}\times 7\times 28$

$=616c{m}^2$.