Perimeter
Perimeter is the total distance around the boundary of a closed shape, found by adding the lengths of all sides. In Grade 6 Saxon Math Course 1, students apply the perimeter formula to various polygons and use it in reverse to find unknown side lengths given the perimeter and other sides. For a rectangle with length 8 cm and width 5 cm: P = 8 + 5 + 8 + 5 = 26 cm, or equivalently P = 2(l + w) = 2(13) = 26 cm. Perimeter is measured in linear units such as centimeters, inches, or feet.
Key Concepts
New Concept The distance around a shape is its perimeter . To find the perimeter of a polygon, we add the lengths of its sides. What’s next This is your introduction to measuring geometric figures. Next, you’ll tackle worked examples to calculate the perimeter of various shapes, including regular polygons, and solve problems from a new perspective.
Common Questions
How do you find the perimeter of any polygon?
Add the lengths of all sides together.
What is the perimeter formula for a rectangle?
P = 2l + 2w = 2(l + w), where l is length and w is width.
Find the perimeter of a rectangle with length 8 cm and width 5 cm.
P = 2(8 + 5) = 2 × 13 = 26 cm.
A pentagon has perimeter 45 cm and four sides of 8, 10, 9, and 7 cm. What is the fifth side?
Fifth side = 45 − (8 + 10 + 9 + 7) = 45 − 34 = 11 cm.
What units are used for perimeter?
Linear units: cm, m, in, ft, etc. Perimeter is a one-dimensional measurement.