1. Geometry :

2. In this lesson, you will learn how to find:

3. Some more terms you need to know:

4. Whenever you divide the distance around a circle by its own diameter, you always get a constant number called “ Pi.” Pi’s is non terminating and non repeating

5. diameter = 2.4 cm Diameter = 7,926 mi Circumference of a quarter = 7.54 cm Circumference of Earth = 24,902 mi 3.14 3.14

6. First, we need to know the diameter of the pizza. Diameter = 18 in Then, we use the following formula: What is the circumference of the pizza ?

7. What if you are only given the radius? C ≈ 56.5 in Remember!

8. Here, we’re given a radius, but we need a diameter to find the circumference of the dart board. So, what should we do to this radius? If you said we need to “double” it, you’re right! Radius = 12 in

9. C = 2 × 3.14 × 12 C ≈ 75.4 in Radius = 12 in

10. Find the circumference for each of the following circles. Round answers to the nearest tenth. 8 ft 1. 3. 7 m 2. 4. C ≈ 50.2 ft C ≈ 22 m 4 in C ≈ 12.6 in C ≈ 12.6 in 10.5 cm C ≈ 65.9 cm or

11. Radius = 3 ft or Remember! Always follow order of operations and simplify exponents FIRST!

12. Do you think we could find the area of say… my face? Do you think we could find the area of say… my face? How do we do this? How do we do this? First, we need to measure the width of your face.

13. It looks like the diameter of your face is about 13 inches. Remember! To find the area, of a circle we need the radius. So, divide the diameter by 2! Diameter = 13 in

14. 6 ft 1. 3. 5.4 cm 2. 4. 9 in 14 km Find the area of each circle below. Round answers to the nearest tenth.

15. Here’s how to find the diameter of circle if you know its circumference. ?

16. Here’s how to find the area of a circle if you know its circumference. First, find the diameter: