1. Perimeter Perimeter is the distance all of the way around an object and is find by adding the lengths of all of the sides together.

2. EXAMPLE Find the perimeter of a square whose side length is 5 meters. We know that a square has four sides, and each is the same length. Therefore, to find the perimeter we would add 5 meters four times: 5m + 5m + 5m + 5m = 20m

3. EXAMPLE How much fencing would be needed to border a yard that is 250 feet long and 100 feet wide? Again, we need to find the perimeter to solve this problem. In this case, we would add 100 ft two times and 250 ft two times because we need to go all of the way around the yard. 250 ft + 250 ft + 100 ft + 100 ft = 700 ft of fencing

4. EXAMPLE Find the perimeter of a triangle that is located at the coordinates (5, 6), (2, 2) and (-2, 5). When you get to an problem like this, always draw it to help you visualize the situation.

5. Cont’d To find the perimeter, we will need to find the distance between each of these points using the distance formula and then add those distances up. The distance formula is: 1. Find the distance between (2, 2) and (5, 6) 2. Find the distance between (5, 6) and (-2, 5) 3. Find the distance between (2, 2) and (-2, 5) So the perimeter is 5 + 7.1 + 5 = 17.1

6. What About Circles? Activity You will need: string and a ruler Remember, the perimeter is the distance all of the way around an object. When we are finding the perimeter of a circle, we give that a special name. We call it the circumference. Take a piece of string and measure its length. In our case our string measure 31.4 cm.

7. Cont’d Take your string and turn it into a circle. Now we have a circle whose circumference is equal to the length of the string, in our case 31.4 cm. Now measure the diameter of the circle. Diameter is the distance across the circle, going through it’s center. Our diameter is 10 cm

8. Cont’d Take your circumference and divide it by the diameter. Here is our equation: Circumference/diameter = 31.4/10 = 3.14 KEY POINT: No matter what you had for your circumference and diameter, when you divide you should always get 3.14!

9. Discovering Pi This special number, rounded to 3.14, is called Pi (pronounced “pie”) and is denoted by the symbol π.