The perimeter of a shape is the distance around the outside of the shape. It is the total length of all the sides of the shape added together.

The formula to find the perimeter of different shapes are:

- For a square or rectangle: P = 2(l + w), where P is the perimeter, l is the length, and w is the width.
- For a triangle: P = a + b + c, where P is the perimeter, and a, b, c are the lengths of the three sides.
- For a circle: P = 2πr, where P is the perimeter, and r is the radius of the circle.

It is important to include the units when expressing the perimeter, such as inches, centimeters, or any other unit of length.

Understanding the concept of perimeter helps in measuring the boundary of a shape, determining the amount of material needed to enclose a space, or calculating the distance around an object.

Study GuidePerimeter Activity LessonArea and Perimeter Worksheet/Answer key

Perimeter Worksheet/Answer key

Perimeter Worksheet/Answer key

Perimeter Worksheet/Answer keyPerimeter

Geometry (NCTM)

Analyze characteristics and properties of two- and three-dimensional geometric shapes and develop mathematical arguments about geometric relationships.

Identify, compare, and analyze attributes of two- and three-dimensional shapes and develop vocabulary to describe the attributes.

Use visualization, spatial reasoning, and geometric modeling to solve problems.

Use geometric models to solve problems in other areas of mathematics, such as number and measurement.

Connections to the Grade 3 Focal Points (NCTM)

Measurement: Students in grade 3 strengthen their understanding of fractions as they confront problems in linear measurement that call for more precision than the whole unit allowed them in their work in grade 2. They develop their facility in measuring with fractional parts of linear units. Students develop measurement concepts and skills through experiences in analyzing attributes and properties of two-dimensional objects. They form an understanding of perimeter as a measurable attribute and select appropriate units, strategies, and tools to solve problems involving perimeter.