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- How are the perimeter formulas similar? How are they different?
- Which formulas could be simplified? Why do you think that is?

To find the perimeter of any shape we can add up all of the side lengths, however the properties of some shapes result in special perimeter forumulas.

Find the perimeter of the isosceles triangle shown.

Worked Solution

Find the perimeter of an equilateral triangle with a side length of 5\text{ mm}.

Worked Solution

Find the side length indicated on the diagram if the perimeter of the shape is 69\text{ cm}.

Worked Solution

In the rectangle ABCD, side AB has a length of 6 units.

a

State the other side of ABCD which must have a length of 6 units.

Worked Solution

b

If another side of the rectangle measures 5 units, find the perimeter.

Worked Solution

Jacob is helping his father build a garden with a fence around it, and they decide to make the garden in the shape of a parallelogram. The garden has one side that is 15 feet long and the side adjacent to it is 10 feet long. What is the total perimeter of the garden fence that Jacob and his father need to prepare?

Worked Solution

Idea summary

To find the perimeter of a figure, add up all of its side lengths.

The perimeter of a triangle, with sides a,\,b,\, and c has the formula: P_\text{triangle} = a + b + c

The perimeter of a parallelogram, with slant height, a, and base, b, has the formula: P_\text{parallelogram} = 2 \left(a+b\right)

The perimeter of a rectangle, with length, l, and width, w, has the formula:P_\text{rectangle} = 2 \left(l+w\right)

The perimeter of a square, with side length, l, has the formula: P_\text{square} = 4 l