Around the outside
Perimeter is all about the distance around the outside, a little like walking around the outside of the school grounds. The perimeter of a polygon (a 2D shape with straight edges) is the total distance around the outside. We can calculate the perimeter of any polygon, no matter how many sides it has. Let's find out how.
Worked Example
Question 1
Find the perimeter of the shape given.
Taking a shortcut!
Rectangles are a special kind of polygon, and they have special features that we can use to work out the perimeter. With two pairs of equal sides, we can work out the perimeter by adding the length and width, and doubling it.
Worked Example
Question 2
Find the perimeter of the rectangle shown.
The power of the perimeter
This is where the perimeter helps us! If we know the perimeter of our rectangle, and the length of one of our sides, it's just one step to work out the length of the missing side.
Worked Example
Question 3
A rectangle has a perimeter of $22$22 cm. If its length is $8$8 cm, what is its width?
Squares are rectangles, but all 4 sides are the same length. This means we can multiply one of the lengths by 4, and find our perimeter.