Title – Congruent and Symmetric shapes

By – Jennifer Looney

Primary Subject – Math

Grade Level – 3rd

Learning Objectives:

• After the lesson, the student will be able to accurately point out what pairs of shapes are congruent and which are not.
  
• The student will be able to use graph paper and rulers to correctly create congruent shapes and shapes that have symmetry.
  
• The student will be able to accurately point out shapes that have symmetry.

Materials needed:

• Construction paper
  
• Graph paper (enough for each student)
  
• Rulers (enough for each student to have one)
  
• Scissors
  
• Markers
  
• White paper or two half pieces of poster board

Pre-Activity Preparation:

• Make examples of symmetric and congruent shapes (an example of each to use when explaining the definitions of symmetric and congruent and smaller examples to use at the end of the lesson).
  
• Make a 1/2 poster for each word (congruent and symmetric) with the definition.
  
• Make an example for the activity.

Transition:

“Please return to your desk and put everything away.”

Introduction:

Hold up a normal pen and then hold up a large pen and ask, “Are these pens the same size?” Then go on to explain the definitions of symmetry and congruent shapes. (You could use two items as long as they are the same thing, but different sizes.

Procedure:

1. Explain that “If two things or shapes are congruent, they are the same shape and the same size.”

2. Hold up an example of two congruent things: “These two shapes are congruent, because they are the same shape and the same size.”

3. Then hold up the example from the introduction and explain that they are not congruent, because although they are the same shape, they are different sizes.

4. Explain that if “something is symmetric, it can be folded in half and match up on both sides.”

5. Then fold a piece of paper in half and cut out a heart – or any other shape – and explain that it has symmetry because it can be folded in half and match up perfectly.

6. Then using a piece of paper (NOT folded in half) cut out another shape.

7. Explain that it is not symmetric because when you fold it in half, it does not match up.

8. Go through more examples, mixing congruent (and non-congruent) with symmetric (and non-symmetric) shapes.

Closure:

After showing all of the examples, have students look around and list things in the classroom that are congruent (i.e. desks, paper, new pencils) and things that are symmetric (i.e. paper). Then explain the activity.

Activity:

Have students use graph paper and rulers to draw a symmetric shape and two congruent shapes. Make sure you have an example ready to show the students.

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Jennifer Looney

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