Plane vs. Solid Geometry

Lesson Plan - Get It!

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Plane vs. Solid Geometry

A ball, an ice cream cone, a house, and a box are all three-dimensional, or 3D, shapes. For example, a ball is round. You can hold it and turn it and touch all around the surface of the ball. But when you draw it, you draw a circle. The circle you drew on your paper is flat.

Same thing with the box. When you hold a box, it has six sides. The 3D box can be filled on the inside. However, when you drew the box, you drew a flat rectangle or square with four sides.

The circle, rectangle, square, and triangle are all examples of plane geometry. These shapes exist in two dimensions (2D).

When you draw a rectangle, for example, it has two measurements: length and width.

These two measurements represent the two-dimensional plane that this shape exists in. A two-dimensional plane is a flat surface, like an endless piece of paper.

Solid shapes, like a box, are different from plane shapes because they have a third dimension.

• Remember the rectangle?

It had two dimensions: length and width. When you drew your picture earlier, the paper you drew on was on a flat surface, like a desk or a table.

Now, a solid shape adds another dimension. This measurement is the height.

Solid shapes are 3D and have length, height, and width.

Types of Plane Shapes

There are two types of plane shapes: polygons and round shapes.

Polygons are two-dimensional plane shapes that are made of straight lines that connect.

For example, a square and rectangle are polygons.

• Can you think of any more?

Triangles, pentagons, trapezoids, parallelograms, hexagons, octagons, rhombus are all examples of polygons and plane shapes.

Round shapes are plane shapes that are two-dimensional and have continuous rounded lines.

Types of Solid Shapes

There are two types of solid shapes: polyhedra and non-polyhedra.

Polyhedras are three-dimensional solid shapes that have flat surfaces. Cubes, pyramids, and prisms are examples of polyhedra solid shapes.

Non-polyhedras are three-dimensional shapes where a surface is not flat, but rounded. Spheres, cones, and cylinders are all examples of these solid shapes.

Now that you know the difference between plane and solid geometry as well as the types of plane and solid shapes, visit the Got It? section to practice identifying these shapes.