Question

The circles have the same centre O. The radius of the inner circle is 3 cm. The width of the shaded region between the inner circle and outer circle is 2 cm. Work out the area of the shaded region. Give your answer correct to 3 significant figures. (3 marks)

Answer 1

50.3 cm²

Explanation:

we are given that the radius of the smaller circle A is 3, and that the width of the shaded portion of circle B, is 2. so, we add 3+2=5 and find that the radius of circle B is 5.

now, we subtract the areas of circles B and A.

use area formula:

`a = \pi {r}^(2)`

for circle B, that would be 5²×π=25π.

for circle A, that would be 3²×π=9π

their difference is (25-9)π=16π.

this is approximately equal to 50.3 cm²