CCSS.Math.Content.1.G.A.1
The standard
Distinguish between defining attributes (e.g., triangles are closed and three-sided) versus non-defining attributes (e.g., color, orientation, overall size); build and draw shapes to possess defining attributes.
Common Core State Standards for Mathematics · Geometry
What this standard means
Students need to tell which features make a shape what it is. A triangle must have three straight sides and be closed. Its color, size, or the way it is turned do not change its name. Students also need to build and draw shapes that match those must-have features.
Mastery looks like sorting mixed shapes and explaining why each belongs. Students should accept “weird” examples, like a skinny triangle or tilted square. Common sticking points are calling a shape by how it looks most familiar, thinking a turned square is not a square, or counting curved edges as sides.
Ways to teach it
- Give students straws and clay, then ask them to build two triangles, two rectangles, and one shape that is not closed.
- Ask, “Can a tiny blue triangle and a huge red triangle both be triangles? Explain using sides and corners.”
- Show five shapes on the board, and have students circle only the closed shapes with four straight sides.
- Have students find shapes on classroom objects, then name one feature that matters and one feature that does not.
Plan a lesson for CCSS.Math.Content.1.G.A.1
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Related standards
- CCSS.Math.Content.2.G.A
Reason with shapes and their attributes.
- 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.3.G.A
Reason with shapes and their attributes.
- CCSS.Math.Content.1.G.A
Reason with shapes and their attributes.