Virginia SOL 3.MG.4.a
The Standard
Describe a polygon as a closed plane figure composed of at least three line segments that do not cross.
Virginia Standards of Learning for Mathematics · The student will identify, describe, classify, compare, combine, and subdivide polygons.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students decide whether a figure is a polygon by checking its sides, closure, and intersections. They explain which defining feature makes each example or nonexample fit.
What Mastery Looks Like
- Students correctly sort examples and nonexamples, even when shapes are rotated or unfamiliar. They justify each choice by checking the sides, closure, and intersections.
Common Misconceptions
- Students may call any flat shape a polygon, including circles, open figures, or figures with crossing sides. They may also think a rotated or irregular shape is not a polygon.
How to Assess It
- Give students six figures, including an open figure, a circle, and a figure with crossing sides. Ask them to circle each polygon and explain one choice.
Lesson moves
Ways to Teach It
Give pairs craft sticks to build three polygons and three nonexamples, then label why each figure belongs in its group.
Show an open figure and ask, "What single change would make this a polygon?" Students draw and explain their change.
Play Polygon Detective with shape cards, awarding a point only when students name evidence for their decision.
Take a classroom photo walk and list objects with polygon faces, then explain why a clock face or curved sign does not qualify.
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Printable 3.MG.4.a Worksheet
A ready-to-print activity worksheet aligned to 3.MG.4.a, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- 6.MG.4.a
Identify regular polygons.
- 3.MG.4.b
Classify figures as polygons or not polygons and justify reasoning.
- 3.MG.4.f
Combine no more than three polygons, where each has three or four sides, and name the resulting polygon (triangles, quadrilaterals, pentagons, hexagons, octagon...
- 3.MG.4.g
Subdivide a three-sided or four-sided polygon into no more than three parts and name the resulting polygons.
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