Geometry: Perimeter of Polygons

In this lesson, we will learn the perimeter of the following polygons:

• square
• rectangle
• parallelogram
• triangle
• rhombus
• trapezoid

We will also learn how to solve word problems involving perimeter of polygons.

Perimeter of Polygons

The perimeter of a polygon is the sum of the lengths of its sides. It is the distance around the outside of the polygon.

See also area of circles, cicumference of circles.

Perimeter of a Square

Since the sides of a square are equal, the perimeter of a square is 4 times the length of its side.

Perimeter of a square = s + s + s + s = 4s

where s is the length of one side

Perimeter of a Rectangle

A rectangle has four sides, with opposite sides being equal in length.

Perimeter of a rectangle = l + l + w + w = 2(l + w),

where l is the length and w is the width of the rectangle.

Worksheet 1, Worksheet 2, Worksheet 3 to calculate the area and perimeter of rectangles.

Perimeter of a Parallelogram

Similar to a rectangle, a parallelogram has four sides with opposite sides being equal in length.

Perimeter of a parallelogram = l + l + w + w = 2(l + w)

where l is the length and w is the width of the parallelogram.

Worksheet to calculate the area and perimeter of parallelograms

Perimeter of a Triangle

Perimeter of a triangle = a + b + c

where a, b and c are the lengths of each side of the triangle.

Perimeter of a Rhombus

A rhombus has 4 equal sides, so the perimeter of a rhombus is 4 times the length of its side.

Perimeter of a rhombus = s + s + s + s = 4s

where s is the length of one side

Perimeter of a Trapezoid

a is parallel to b

Perimeter of a trapezoid = a + b + c + d

where a, b, c and d are the lengths of each side.

The following video shows how to find the Perimeter of a Rectangle

The following video shows how to find the Perimeter of a Parallelogram

The following video shows how to find the Perimeter of a Trapezoid

The following video shows how to find the perimeters of rectangles, squares, triangles and other polygons.

Word Problems involving perimeter of polygons

A rectangle is three times as long as it is wide. If the perimeter is 62 cm, what is the length?

The width of a rectangle is 6 cm less than the length. If the perimeter is 52 cm, what is the width?

The length of a rectangle is 7 cm more than 4 times its width. It perimeter is 124 cm. Find its dimensions.

The width of a rectangle is 4 ft smaller than 3 times its length. Its perimeter is 144 ft. Find its dimensions.

A rectangle garden is 2.5 times as long as it is wide. It has a perimeter of 1.6 feet. How long and wide is the garden?

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