standard_description: 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.
problem_activity: Narrative
This warm-up prompts students to carefully analyze and compare attributes of two-dimensional figures with attention to the number of sides, symmetry, and presence of parallel and perpendicular lines. The activity enables the teacher to observe the attributes that students notice intuitively and hear the terminologies they feel comfortable using.
Launch
Groups of 2
Display the image.
“Pick one that doesn’t belong. Be ready to share why it doesn’t belong.”
1 minute: quiet think time
Activity
“Discuss your thinking with your partner.”
2–3 minutes: partner discussion
Share and record responses.
Student Facing
Which one doesn’t belong?
[IMG]
Student Response
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Activity Synthesis
If no students mention parallel sides as an attribute to consider, ask them about it.
Consider asking: “Let’s find at least one reason why each one doesn’t belong.”


aligns: yes