9.02 Perimeter

Can you  add multiple numbers  together?

Examples

The perimeter of a shape is the length around the outside of the shape.

If a shape is made up of unit squares, we can use those to count the distance around the outside of the whole shape. We count the outside edges of every unit square, making sure we include the whole outside of our shape.

Examples

Example 2

Find the perimeter of the shaded region shown, where each square has a length of 1 unit.

Worked Solution

Create a strategy

We can count the unit edges outside the shaded shape.

Apply the idea

The shape has 10 unit edges around it.

Perimeter =10 units

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2D shapes are also known as polygons, and we've seen some of these shapes before. This video looks at how to work out the perimeter of any polygon.

Examples

Example 3

Find the perimeter of the figure shown.

Worked Solution

Create a strategy

Add all the lengths of the sides to find the perimeter.

Apply the idea

\displaystyle \text{Perimeter}	\displaystyle =	\displaystyle 4 + 8 + 8 + 16 + 12	Add the lengths of the sides
	\displaystyle =	\displaystyle 48 \text{ m}

Watch question walkthrough