CCSS.Math.Content.3.G.A.1
The standard
Understand 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 (e.g., quadrilaterals). Recognize rhombuses, rectangles, and squares as examples of quadrilaterals, and draw examples of quadrilaterals that do not belong to any of these subcategories.
Common Core State Standards for Mathematics · Geometry
What this standard means
Students need to sort and name shapes by their attributes, not by how they look at first glance. They should know that a shape can belong to more than one group, such as a square being a rectangle and a quadrilateral.
Mastery looks like explaining why a shape fits a group using sides, angles, and parallel lines. Students often get stuck thinking a shape stops being a rectangle if it is tilted, or that squares are not rectangles. They may also overuse visual clues instead of checking attributes.
Ways to teach it
- Give pairs shape cards to sort into quadrilaterals, rectangles, rhombuses, squares, and “other,” then have them defend one tricky placement.
- Ask students to write: Is every square a rectangle, and is every rectangle a square? Explain with attributes, not pictures.
- Show five shapes, including a tilted rectangle and an irregular quadrilateral, and have students label all groups each shape belongs to.
- Have students find quadrilaterals in classroom objects, then sketch one that is not a square, rectangle, or rhombus.
Plan a lesson for CCSS.Math.Content.3.G.A.1
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Related standards
- CCSS.Math.Content.5.G.B.3
Understand that attributes belonging to a category of two-dimensional figures also belong to all subcategories of that category.
- CCSS.Math.Content.2.G.A.1
Recognize and draw shapes having specified attributes, such as a given number of angles or a given number of equal faces. Identify triangles, quadrilaterals, pe...
- CCSS.Math.Content.1.G.A.1
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- CCSS.Math.Content.K.G.A
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