Question

from a circular piece of cardboard of radius 3 CM ,3 sectors of central angle 40 degree have been cut off. Find the area of the remaining portion

Answer 1

The sum of areas of three identical sectors each of central angle $40^\circ=\frac{2\pi}{9}$ at the center of circle

$=3\times\frac{2\pi}{9}\times 3^2$

$=6\pi$

Now, the area of remaining portion

$=\pi\times 3^2-6\pi$

$=3\pi{\text}{unit}^2$