Unit 4B Measure Figures Lesson 1 Circumference

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

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.

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

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

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 = ____

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.

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

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.

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

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

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

Homework