Question

Circle A has radius 4 feet. Circle B has radius 9 feet. What is the ratio of the area of circle A to the area of circle B?

23

49

827

1681

Answer 1

`\large\boxed{(16)/(81)}`

Explanation:

The formula of an area of a circle:

`A=\pi r^2`

r - radius

Circle A:

radius = 4 ft. Substitute:

`A_A=\pi(4^2)=16\pi\ ft^2`

Circle B:

radius = 9 ft. Substitute:

`A_B=\pi(9^2)=81\pi\ ft^2`

The ratio:

`(A_A)/(A_B)=(16)/(81)`