1. Area of Circles

2. Area of Circles
To find the area of a Circle, we use the formula:
A = π*r²

3. Examples
The distance of intense shaking from the epicenter of a particular earthquake to the outer edge was about 1.4 miles. To the nearest square mile, what was the area of intense shaking? Use 3.14 for π

4. Examples
What is the area of a circle with a radius of 3.2 ft? Leave your answer in terms of π.

5. Examples
The diameter of the eye of a certain hurricane was 30 miles. To the nearest square mile, what was the area of the eye? Use 3.14 for π..

6. Examples
Bubble netting is a hunting technique used by humpback whales. They blow bubbles in a circular ring that drives fish toward the center of the circle. What is the area of a ring of bubbles 100 feet wide? Use 3.14 for π

7. Examples
One crop circle has a diameter of 40 feet and another has a diameter of 80 feet. Is the area of the larger crop circle twice that of the smaller circle? Justify your answer.

8. Examples SMALLER CIRCLE LARGER CIRCLE A = πr² A = πr² A = π (20) (20)
A = 400π ft²
LARGER CIRCLE
A = πr²
A = π (40) (40)
A = 1600π ft²

9. Examples
Find the ratio of the area of the larger circle to the area of the smaller circle.
1600π/400π = 4/1
So, the area of the larger circle is 4 times that of the smaller circle.

10. Examples
How many smaller circles do you need to make the area of the larger circle?

11. Examples LARGER CIRCLE SMALLER CIRCLE A = πr² A = πr² A = π (6) (6)
A = 4π ft²
LARGER CIRCLE
A = πr²
A = π (6) (6)
A = 36π ft²

12. Find the ratio of the area of the larger circle to the area of the smaller circle.
36π = 9
You need nine smaller circles to equal the area of the larger circle. 4π 1
Examples

13. A = π*r²
d = 2r
Review:
Homework:
Area of Circles Worksheet