1. Area and Circumference of Circles

2. Circumference of a Circle Formula to MEMORIZE!!!! OR

3. What do the letters stand for? C = circumference r = radius of the circle d = diameter of the circle π = pi. The value of πis “3.14”

4. Area of a Circle Formula to MEMORIZE!!!!

5. What do the letters stand for? A = area r = radius of the circle π = pi. The value of πis “3.14”

6. Question 1 When looking for area, and you only have the diameter, what is the FIRST thing you must do? * Split the diameter in half to get the radius.

7. Question 2 What is another name for circumference of a circle? * Perimeter!

8. Example 1 Find the area of a circle with a diameter of 24 in. Answer:

9. Example 2 Find the circumference of a circle with a diameter of 20 m. Answer:

10. Example 3 Find the area of a circle with a radius of 6 cm. Answer:

11. Example 4 Find the circumference of a circle with a radius of 4 km. Answer:

12. Example 5 The circumference of a circle is 120 mi. What is the diameter to the nearest tenth. Answer:

13. Example 6 The circumference of a circle is 72 m. What is the radius to the nearest tenth. Answer:

14. Question What do you notice about the labels between area and circumference? - Area has a squared sign on the unit, but circumference does not.

15. Question Why do you think the area label has the squared sign? - To find the area, you must ‘square’ the radius.

16. Challenge What is the area of the square if a circle with a radius of 4 in. is inscribed in a square? 4 in Answer: 64 in 2