1. Unit 4B Measure Figures
Lesson 1 Circumference

2. Lesson 1: Circumference
Objective: Swbat find the circumference of a circle. Do Now:

3. Lesson 1: Circumference
Definitions A circle is a set of all points in a plane that are the same distance from a point, called the center. The circumference is the distance around the circle. The diameter is the distance across the circle through its center . The radius is the distance from the center to any point on the circle. Pi (∏) is an irrational number that is approximately 3.14.

4. Lesson 1: Circumference
The diameter, d of a circle is twice its radius, r . The radius, r is half of its diameter d. d = 2r r = ½ d diameter center radius

5. Lesson 1: Circumference
1.) Diameter = 14 Radius = __________ 2.) Radius = 8 Diameter = ________

6. Lesson 1: Circumference
Find the radius or diameter of each circle with the given dimension. 3.) d = 23 r = ____ 4.) r = 3 d = ____ 5.) d = 16 r = ____ 6.) r = 5.2 d = ____

7. Lesson 1: Circumference
Circumference of a Circle Circumference of a circle is equal to pi times the Diameter or pi times twice its radius. C = ∏d or C = 2∏r Example: C = ∏(10) = 31.4 in. C = 2∏(5) = 10∏ = 31.4
10 in.
5 in.

8. Lesson 1: Circumference
Try It! C = ∏d or C = 2∏r a. b.
21 in.
3 in.

9. Lesson 1: Circumference
Real-World Problem Big Ben is a famous clock tower in London, England. The diameter of the clock face is 23 feet. Find the circumference of the clock face. Round to the nearest tenth.

10. Classwork Guided Practice #1 - 6 Independent Practice #1 - 9
Problem Solving Practice #1 - 6

11. Closure Question: How do you find the circumference of a circle?
Exit Ticket
Homework: Practice #1 - 17

12. Exit Ticket Find the circumference of a circle when:
The diameter is 8 in.
The radius is 3 in.

13. Homework