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Grade 5 Math · World 9: Polygon Palace · Level 91
Properties Pass Down
Reason that all squares have four right angles because all squares are rectangles.
Warm-up, learn, try it together, practice, then a quick check. About 15 minutes.
What children learn in Level 91
- Here's a powerful idea. If something is true of a whole group, it's true of every member of that group.
- All rectangles have four right angles. Squares are rectangles. So all squares have four right angles. We don't even need to measure!
- It only goes down, not up. All squares have four equal sides, but that doesn't mean all rectangles do.
- So when you meet a new shape, ask: what group does it belong to? It gets everything that group has.
Georgia's K-12 Mathematics Standards:
- 5.GSR.8.2 — Determine, through exploration and investigation, that attributes belonging to a category of two-dimensional figures also belong to all subcategories of that category.