Symmetry in Figures (Part 1)
10 min
Narrative
The purpose of this Warm-up is to elicit the idea of mirror images that match exactly, which will be useful when students generate a definition for symmetry in a later activity. Students may notice and wonder about possible real-life objects the block structure represents, but focus the discussion on describing how the two halves are reflections of each other.
Elicit the term “symmetry” or language that describes attributes of line-symmetric figures.
Launch
- Groups of 2
- Display the image.
- “What do you notice? What do you wonder?”
- 1 minute: quiet think time
Teacher Instructions
- “Discuss your thinking with your partner.”
- 1 minute: partner discussion
- Share and record responses.
Student Task
What do you notice? What do you wonder?
an image composed of pattern blocks. left and right sides of pattern are the same. each side has 2 green triangles, 2 blue parallelograms, 4 tan rhombuses, 2 red trapezoids, 2 yellow hexagons.
Sample Response
Students may notice:
- The left and right halves mirror each other.
- The top and bottom halves mirror each other.
- The same set of figures are on each side of the image: 2 hexagons, 2 rhombuses, 2 triangles, 2 trapezoids, 4 narrow rhombuses.
- The figures are pieces of pattern blocks.
- Are all pattern blocks of the same figure exactly the same size?
- If we fold the image along a vertical line through the center point, would the two sides match up exactly?
- Does the arrangement represent something?
Synthesis
- Highlight the language students used to describe the symmetry in the design such as:
- Mirror images
- The same parts on both sides of the image
- “How might we check to see if the part on the left and the part on the right are the same?” (We could place each half of the image on top of the other to see if they match.)
Standards
Addressing
- 4.G.3·Recognize a line of symmetry for a two-dimensional figure as a line across the figure such that the figure can be folded along the line into matching parts. Identify line-symmetric figures and draw lines of symmetry.
- 4.G.A.3·Recognize a line of symmetry for a two-dimensional figure as a line across the figure such that the figure can be folded along the line into matching parts. Identify line-symmetric figures and draw lines of symmetry.