Lesson 3 of 9
Some counts make neat shapes
Show on a big screen9 coins on the floor: 3 rows of 3. No coin left over, no gap anywhere. Nine makes a square. Rows go across. Columns go up and down.
Step 1 of 4
- 9 dots make a square: 3 rows of 3.
- 6 dots make a triangle: rows of 1, 2, 3.
- 8 dots make a rectangle: 2 rows of 4.
- 7 dots make only one row. No square, no triangle.
A count with equal rows and columns is a square number. Like 1, 4, 9, 16, 25.
A count that makes a triangle is a triangular number. Each row is one longer than the last. Like 1, 3, 6, 10. The next triangle adds a longer row. 1 + 2 = 3. 3 + 3 = 6. 6 + 4 = 10.
Some counts make a rectangle: unequal rows and columns, still tidy. 8 dots make 2 rows of 4. A count can fit two shapes. 6 dots make a triangle, and also 2 rows of 3.
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