3D Shapes
Lessons in this chapter
About 3D Shapes
Solids Are Also Shapes is the chapter where kids notice that a ball and a box are mathematical objects too, with names and properties of their own.
Identify Cubes and Cuboids starts with the two solids kids handle most, because almost every box in a house is one or the other. The distinction is simple to state and genuinely useful: a cube has six identical square faces, a cuboid has rectangular ones, so a dice is a cube and a cereal box is a cuboid.
Identify Cones, Cylinders and Spheres covers the curved solids. A cone tapers to a point, a cylinder has two flat circular ends, a sphere is curved all the way round with no flat face at all. Kids can test each one by trying to stand it up or roll it, which is a far better memory aid than a labeled diagram.
With only two lessons, this is a short chapter, but it carries the first real idea of a face: the flat 2D shape you find on the surface of a solid. That is what connects it back to 2D Shapes, and it is what later grades build on when they get to surface area.
Both lessons, Identify Cubes and Cuboids and Identify Cones, Cylinders and Spheres, open as worksheets in the page. The questions show solids from more than one angle, so a child has to recognize the object rather than remember a single picture of it. It is a short chapter, free to practice online, and a reasonable one sitting.
Frequently asked questions
Two lessons. Identify Cubes and Cuboids comes first, since a cuboid is the box shape children see most often, and Identify Cones, Cylinders and Spheres follows with the solids that have a curved surface. Both sit in the Common Core kindergarten Geometry domain (K.G), alongside the flat shapes.
A 2D shape is flat, like a drawn square. A 3D shape is solid and takes up space, like a cube you can hold. The easiest check for a kindergartener is whether you could pick it up.
Cube, cuboid, cone, cylinder and sphere. Those five cover nearly everything a child will be asked to name at this stage.
Both have six flat faces and square corners. A cube's faces are all identical squares, so a dice is a cube. A cuboid's faces are rectangles, so a cereal box is a cuboid.
Count the flat ends. A cylinder has two flat circles, one at each end, so it stands up either way round. A cone has one flat circle and comes to a point, so it only stands one way.
A flat surface on a solid shape. A cube has six, a cylinder has two, a sphere has none. Faces are what link this chapter back to 2D Shapes, because each face is one of the flat shapes kids already named.