1. Ms. Cuervo CAHSEE Prep CIRCUMFERENCE

2. Circumference 7MG 1.2 Students will use pi to find the circumference and diameter of circles. VOCABULARY Circumference: The distance around a circle Diameter: A line segment connecting two points on a circle and passing through the the center of the circle – the diameter is twice the length of the radius Radius – the radius is half the length of the diameter

3. Pi = circumference ÷ diameter When pi is written out as a decimal, the digits following the decimal point are endless. We use the approximations 3.14 and 22/7 for the value of pi. If you know the diameter of a circle, how can pi help you find the circumference? Pi × diameter = circumference

4. Circumference The distance around a circle is called the circumference. Circumference is similar to perimeter (distance around a shape). Perimeter describes the distance around a polygon. Circumference describes the distance around a circle. The distance across a circle has a special name: the diameter. The radius is half the diameter. Circumference = pi × diameter C = pi × d

5. After years of use, the tiling around the rim of the tub needs to be replaced. You need to determine the circumference of the tub in order to purchase the correct amount of tiles. You know that the radius is 3 feet. What is the circumference?

6. What is the radius of the hot tub? What is the diameter of the hot tub? How can you find the circumference if you know the diameter? What is the approximate value of pi? What is the approximate circumference of the hot tub? 3 feet 6 feet C = pi × d 3.14 or 22/7 C = pi x d C = (3.14) x 6 C = 18.84 feet * In your own words, explain how to solve this problem.

7. The button on your favorite coat fell off and you want to replace it with a new button. You know the circumference of the button is 6.28 centimeters. What is the diameter of the button? What information is given? What is the approximate diameter of the button?

8. How can we solve this? C = pi x d -Instead of solving for c, you need to solve for d. 6.28 = 3.14 x d -Substitute the values provided (circumference and pi) 6.28 = 3.14d 3.14 3.14 -Divide by 3.14 to solve for d. d = 2 * In your own words, explain how to solve this problem.