3rd Grade Math Lesson

Fencing the Animal Sanctuary: Perimeter, Area, and Missing Sides

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3rd GradeBTC Vertical Whiteboard FramingCCSS.3.MD.D.850 min

Learning Objective

Students will be able to calculate the perimeter of polygons by adding all side lengths, distinguish perimeter from area, and determine unknown side lengths of rectilinear polygons given total perimeter and known sides.

Lesson Overview

Students work in random groups of 3 at vertical non-permanent surfaces to discover how to calculate perimeter by adding side lengths, distinguish perimeter from area, and solve for unknown side lengths on rectilinear polygons — all in the context of designing animal enclosures at a sanctuary.

Materials

Vertical whiteboards or large chart paper (one per group)
Dry-erase markers in 2 colors per group
Erasers or paper towels
Random grouping cards or sticks
Printed task cards (one set per group)
Student consolidation note sheets (one per student)
Rulers for reference (optional)

Scaffolded Task Progression

1Task 1

The sanctuary needs to fence a small rabbit pen. Here is the blueprint:

[ Interactive graph / diagram — available in the full lesson ]

How many meters of fencing does the sanctuary need to go all the way around this rabbit pen? Show your work on the whiteboard.

2Task 2

Now the sanctuary needs fencing for a triangular goat pen. Here is the blueprint:

[ Interactive graph / diagram — available in the full lesson ]

How many meters of fencing does the sanctuary need for this triangular pen? Show your work.

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