Maryland Math 3.GR.B.5
The Standard
Explain that shapes in different categories (e.g., rhombuses, rectangles, and others) may share attributes (e.g., having four sides), and that the shared attributes can define a larger category of shapes (e.g., quadrilaterals).
Maryland College and Career Ready Standards for Mathematics (2025) · REASON WITH SHAPES AND THEIR ATTRIBUTES.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students group shapes by features they can point to, such as straight sides and square corners. They explain how shapes with different names can fit in the same group.
What Mastery Looks Like
- A student can identify a square, a long rectangle, and a slanted rhombus as quadrilaterals because each has four straight sides. They can explain that a square is also a rectangle and a rhombus.
Common Misconceptions
- Students may think turning a square changes its name, or that a square cannot also be a rectangle. They may count a shape with a curved edge or an open gap as a quadrilateral.
How to Assess It
- Draw a rectangle and a slanted rhombus on an exit ticket. Ask, 'What larger shape group includes both? What feature tells you?'
Lesson moves
Ways to Teach It
Give pairs paper squares, long rectangles, and slanted rhombuses; have them trace the sides and group all three as quadrilaterals.
Show a square and ask, 'Can it belong to both the rectangle group and the rhombus group? How do you know?'
Play a shape-card sort: students place closed figures with four straight sides in a quadrilateral pile and explain one choice.
Show photos of a window and a diamond-shaped traffic sign; students trace their outlines and explain why both are quadrilaterals.
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Related Standards
- 5.GR.B.2
Explain that attributes belonging to a category of two-dimensional figures also belong to all subcategories of that category (e.g., all rectangles have four rig...
- 1.GR.B.3
Distinguish between defining attributes (e.g., triangles are closed and three-sided) versus non-defining attributes (e.g., color, orientation, overall size).
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