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.
Your children can practice using this finding the perimeter worksheet
Students progress to adding the lengths that are labelled in number form for every side.
This perimeter worksheet allows your children to practice finding the perimeter by adding the lengths of each side.
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.
Problems can also be presented with perimeter given and the challenge find or calculate the "missing" lengths. This perimeter worksheet allows your children to practice finding the lengths of the missing side given the perimeter.