standard_description: Use the properties of similarity transformations to establish the AA criterion for two triangles to be similar.
problem_activity: Narrative
This warm-up prompts students to carefully compare 4 shapes. The shapes are designed so that students may compare the color of the shapes as well as geometric attributes.
Launch
Groups of 2
Display the image.
“Pick one that doesn’t belong. Be ready to share why it doesn’t belong.”
Activity
30 seconds: quiet think time
30 seconds: partner discussion
Share and record responses.
Student Facing
Which one doesn’t belong?
A
[IMG]
B
[IMG]
C
[IMG]
D
[IMG]
Student Response
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Activity Synthesis
Display shapes A and B.
“What is alike, or the same, about these shapes?” (They both have three sides. They are both triangles. They are both red.)
“What is different about these shapes?” (One is colored in and one is not. One is smaller or skinnier.)


aligns: no