CCSS.Math.Content.K.G.A.3
The standard
Identify shapes as two-dimensional (lying in a plane, "flat") or three-dimensional ("solid").
Common Core State Standards for Mathematics · Geometry
What this standard means
Students need to sort shapes into flat shapes and solid shapes. They should know that circles, squares, triangles, rectangles, and hexagons are flat. Cubes, cones, cylinders, and spheres are solid. They also need to use simple words like flat, solid, roll, stack, face, corner, and edge.
Mastery looks like a child picking up a shape card or object and saying whether it is flat or solid, then giving a reason. Common mix-ups happen with pictures of solid shapes, like calling a drawn cube flat, or thinking a circle and sphere are the same because both are round.
Ways to teach it
- Set out shape cards and real objects, then have students sort them onto two mats labeled flat and solid.
- Ask, “How do you know this shape is flat or solid?” and have students answer with one reason to a partner.
- Hold up five shapes or objects, and have students show one finger for flat and two fingers for solid.
- Take a classroom shape walk, finding flat shapes on signs and solid shapes in blocks, cans, balls, and boxes.
Plan a lesson for CCSS.Math.Content.K.G.A.3
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