Sort Triangles
10 min
Narrative
This Warm-up prompts students to estimate the measure of an angle in a triangle. This will be important as they classify triangles in this lesson so they will need to distinguish acute, right, and obtuse angles. They will not need to measure angles explicitly but recalling angle measure will help them distinguish the different types of triangles.
Launch
- Groups of 2
- Display the image.
- “What is an estimate that’s too high? Too low? About right?”
- 1 minute: quiet think time
Teacher Instructions
- “Discuss your thinking with your partner.”
- 1 minute: partner discussion
- Record responses.
Student Task
What is the measure of Angle A?
Record an estimate that is:
| too low | about right | too high |
|---|---|---|
Sample Response
Sample responses:
- Too low: 90
- About right: 100 to 120
- Too high: 150
Activity Synthesis (Teacher Notes)
- “How do we know the angle is more than 90 degrees?” (90 degrees is a right angle and this angle is obtuse. It's more than a right angle.)
- “How do we know the angle is less than 180 degrees?” (180 degrees is a straight line and this bends inward so it’s less than 180 degrees.)
Standards
- 5.G.4·Classify two-dimensional figures in a hierarchy based on properties.
- 5.G.B.4·Classify two-dimensional figures in a hierarchy based on properties.
20 min
15 min
Knowledge Components
All skills for this lesson
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Sort Triangles
10 min
Narrative
This Warm-up prompts students to estimate the measure of an angle in a triangle. This will be important as they classify triangles in this lesson so they will need to distinguish acute, right, and obtuse angles. They will not need to measure angles explicitly but recalling angle measure will help them distinguish the different types of triangles.
Launch
- Groups of 2
- Display the image.
- “What is an estimate that’s too high? Too low? About right?”
- 1 minute: quiet think time
Teacher Instructions
- “Discuss your thinking with your partner.”
- 1 minute: partner discussion
- Record responses.
Student Task
What is the measure of Angle A?
Record an estimate that is:
| too low | about right | too high |
|---|---|---|
Sample Response
Sample responses:
- Too low: 90
- About right: 100 to 120
- Too high: 150
Activity Synthesis (Teacher Notes)
- “How do we know the angle is more than 90 degrees?” (90 degrees is a right angle and this angle is obtuse. It's more than a right angle.)
- “How do we know the angle is less than 180 degrees?” (180 degrees is a straight line and this bends inward so it’s less than 180 degrees.)
Standards
- 5.G.4·Classify two-dimensional figures in a hierarchy based on properties.
- 5.G.B.4·Classify two-dimensional figures in a hierarchy based on properties.