Perimeter Examples in Math

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Perimeter.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Math.

Concept Recap

The total distance around the outside of a two-dimensional shape, found by adding all its side lengths.

If an ant walked around the edge of a rectangle, perimeter is how far it walked.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Perimeter is one-dimensional—it's a length around, not space inside.

Common stuck point: Don't confuse with area—perimeter is the edge, area is the inside.

Sense of Study hint: Try tracing your finger around the outside edge of the shape and adding up each side length as you go.

Worked Examples

Example 1

easy
Find the perimeter of a rectangle with length 8 cm and width 5 cm.

Solution

  1. 1
    Recall the perimeter formula for a rectangle: P = 2l + 2w.
  2. 2
    Substitute the values: P = 2(8) + 2(5) = 16 + 10 = 26.
  3. 3
    The perimeter is 26 cm.

Answer

P = 26 \text{ cm}
The perimeter of any polygon is the total distance around its boundary. For a rectangle, opposite sides are equal, so we add two lengths and two widths.

Example 2

medium
A triangle has sides measuring 7 cm, 10 cm, and 12 cm. Find its perimeter.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Find the perimeter of a square with side length 9 m.

Example 2

medium
The length of a rectangle is 3 m more than twice its width. If its perimeter is 42 m, find the length and width.
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Background Knowledge

These ideas may be useful before you work through the harder examples.

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