Recognizing simple symmetry

General

Students learn to recognize simple symmetry.

Standards

CCSS.Math.Content.4.G.A.3

Learning objective

Students will be able to recognize simple symmetry.

Introduction

Ask students to find objects in the classroom that have the same shapes as the shapes on the interactive whiteboard. Then ask students if they can name the shapes. (cube, sphere, and cuboid)

Instruction

Explain to students that a shape has symmetry if it stays the same when a mirror is placed on the midline of a shape. Show a few shapes on the interactive whiteboard. You can also hand out a photocopied sheet of paper with the same images on it, or ask students to draw the objects in their notebooks/on a mini whiteboard. Have students follow along with your explanations on their own shapes. Take the shapes one at a time and explain and show what happens when you place a mirror on the midline of the shape. A few of the shapes have symmetry and a few don't. Hand out a sheet of paper with the image of a triangle to the students. Then give them a mirror. Have students place the mirror on the midline and have them check to see if it has symmetry. In pairs, have students discuss if the shapes on the interactive whiteboard have symmetry or not. Then students must determine which objects do not have symmetry and throw them in the trash can. Have students explain their thinking and how they know it does not have symmetry. Finally students are shown a shape and they must determine which of the three given images is the correct mirror image of the given shape. You can choose to hand out copies of the shape or have students draw it themselves to try drawing the symmetry.

Check that students are able to recognize simple symmetry by asking the following questions:
- What is symmetry?
- Which tool can you use to help determine if a shape has symmetry or not?

Quiz

Students are given shapes and asked to determine, after placing a mirror in the middle, if shapes stay the same, if shapes stay the same, or which shape they would see based on symmetry.

Closing

Discuss with students that it is useful to be able to recognize shapes that have symmetry. To close the lesson, have students determine which of the statements shown is correct regarding the symmetry of a shape.

Teaching tips

Students who have difficulty with this learning goal can be supported by making use of a mirror on all shapes. When they become more comfortable they will be able to recognize symmetry without the mirror.