Classifying Plane Figures

Lesson Plan - Get It!

Audio:

Plane figures are flat figures that can be drawn on a surface, such as squares, rectangles, triangles, and circles.

• Were you able find a lot of them in the images above?

Good job!

• Did you know they're made of line segments and can be closed or open?

Watch the video Plane Figures| Maths for Kids| Grade 3 by Periwinkle to learn more!

While you're watching, write down your answers to these questions:

• What is a plane?
• What do we call the shapes drawn on a plane?
• What are the 2 types of plane figures?
• How can we tell if a figure is open?
• Is a curve open or closed?
• Is an angle open or closed?
• How can we tell if a figure is closed?
• What is the name of point where 2 sides meet?

Let's practice identifying open and closed figures!

We can classify these figures (sort them into groups) by:

• whether they're open or closed
• the number of sides
• the number of vertices
• whether the side lengths are the same or different

You learned that the place where two sides meet are called vertices. (One is a vertex; two or more are vertices.)

Let's look at some figures, and see how many sides and vertices they have:

Polygons

A flat, closed shape, with straight sides, is called a polygon. Many different shapes are polygons. Their sides may be equal, or not.

• Is a circle a polygon?

No. It is flat and closed, but it doesn't have straight sides.

Let's learn more about polygons by watching Naming Polygons- Maths Tutorials from missnorledge.

Rhombus

A rhombus is a flat shape with 4 equal sides.

• Wait, isn't that what we call a square?

Yes, a square is a rhombus with equal angles. But the angles of a rhombus don't have to be equal.

Here's what a rhombus looks like:

If you said, "Hey, that's a diamond!" you are correct. A diamond shape is a rhombus.

Trapezoid

Just one more shape to learn, and that is a trapezoid. A trapezoid is a quadrilateral.

• Do you remember what that is?

Yes, it's a 4-sided figure.

A trapezoid's special feature is that it only has one set of parallel sides. The other sides are not parallel.

Wow! You learned a lot about plane figures, and even met some strange figures with funny names.

• Are you ready to practice what you learned?

Great! Move on to the Got It? page, where you'll get to draw all these shapes and practice identifying them!