Perimeter
Part of the Expressions & Data section of Coddy's Pre-Algebra journey. Lesson 43 of 52.
The perimeter of a shape is the distance all the way around its edge. Walk once around a triangular park with sides of 30, 40 and 50 metres and you cover 30 + 40 + 50, which is 120 metres.
For any shape with straight sides, add every side once. Shapes with equal sides give shortcuts: a rectangle has two lengths and two widths, which is where 2 lengths plus 2 widths comes from, and a square with side 6 has perimeter 4 × 6, which is 24.
A perimeter is a length, so it is measured in metres, feet or centimetres. The usual slip on a shape with many sides is missing one. Count the sides first, then check that you added that many numbers.
Challenge
A five-sided garden has sides of 12, 15, 9, 10 and 14 metres. Find the length of fence P, in metres, needed to go all the way around it.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Expressions & Data
1Variables and Expressions
What a Variable IsWriting ExpressionsExpressions from StoriesTwo OperationsRecap: Expressions2Evaluating Expressions
Substituting a ValueNegative InputsPowers in ExpressionsFormulasRecap: Evaluating5Patterns and Sequences
Continuing a PatternThe Common DifferenceThe nth TermWriting the RuleRecap: Sequences3The Distributive Property
Number PropertiesMental MathDistributing LettersDistributing a MinusRecap: Distributing9Perimeter and Area
PerimeterArea of a RectangleArea of a TrianglePerimeter as an ExpressionRecap: Perimeter and Area