Question

The sector in the given image is half of a quarter circle. The radius of the sector is 10 cm. If it rotates 90° clockwise about its centre, what is the total area (in c m 2 ) swept by it?

a 25
b 37.5
c 42.5
d 50

Answer 1

(☞ﾟ∀ﾟ)☞Answer

The sector in the given image is half of a quarter circle. The radius of the sector is 10 cm. If it rotates 90° clockwise about its centre, what is the total area (in c m 2 ) swept by it?

the correct answer is

(b 37.5

Answer 2

Given the image sector is half of a quarter circle and the radius of the sector is 10 cm.

We have to find the area of f it rotates 90° clockwise about its center

We need to recall the following formula to solve

Quarter circle area is $=\frac{\pi r^2}{4}$

Where r is the radius of the circle.

If we rotates half of a quarter circle 90° clockwise then it will be 3/2 quarter circle

then area is $=\frac{3\pi r^2}{8}$

                    $=\frac{3\pi (10)^2}{8}$

                    $=\frac{75\pi }{2}$

                   $=37.5\pi$