Introduction

In 3rd grade students' work includes solving real-life problems involving perimeters of various polygons. Initially perimeters are found from diagrams by counting the unit lengths that are shown.A 6 x 3 rectangle with the perimeter shown as being 18 steps around.

Your children can practice using this finding the perimeter worksheet worksheet icon

Students progress to adding the lengths that are labelled in number form for every side.A 4 x 7 dimensioned rectangle with perimeter calculation

This perimeter worksheet worksheet icon allows your children to practice finding the perimeter by adding the lengths of each side.

Symbols for congruence

When deriving dimensions your children will need to become familiar with symbols that are used describe the relationship between a shape's sides. Hatch marks are commonly used to show sides of equal length (one or more short line or tick marks through all the lines that are of equal length). Feathers (arrow heads) are used in a similar way to show sides that are parallel.

An example of how the right angle symbol is used in a rectangle
An example of how hatch marks are used to show sides of equal length
An example of how feathers/ arrows are used to show parallel lines

Perimeter From Minimal Dimensions

This worksheet worksheet icon provides practice with finding the perimeter of shapes when only minimal dimensions are given. Be alert to a common student error of just adding the two dimensions given for a quadrilateral.

A rectangle with height and width annotated and a note about how the opposite sides can be derived

Perimeter known, side unknown

Problems can also be presented with perimeter given and the challenge find or calculate the "missing" lengths. A trapezoid with a given perimeter and a calculation showing how the missing length can be found This perimeter worksheet worksheet icon allows your children to practice finding the lengths of the missing side given the perimeter.