Lesson 12
Partition Rectangles into Squares
Lesson Purpose
The purpose of this lesson is for students to partition rectangles into equalsize squares.
Lesson Narrative
Students have arranged tiles to make arrays and rectangles, represented their rectangles by shading squares on a grid, and completed the partitioning of rectangles into equalsize squares. In this lesson, students partition rectangles into equalsize squares with and without guiding marks and represent the total number of squares within the rectangles with equations that show the sum of the number of squares in each row or the number of squares in each column. Monitor for the ways students use what they know about the structure of arrays to plan and partition their rectangles. It is not important that students partition the rectangles into exactly equalsize squares.
 Action and Expression
 MLR2
Learning Goals
Teacher Facing
 Partition rectangles into rows and columns of equalsize squares, and count to find the total number of squares.
Student Facing
 Let’s partition rectangles into squares.
Required Materials
Materials to Gather
Required Preparation
Lesson Timeline
Warmup  10 min 
Activity 1  15 min 
Activity 2  20 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
How did the work of arranging objects to make arrays support the understanding of partitioning rectangles into equalsize squares? What additional support is needed as students build this understanding?
Suggested Centers
 Write Numbers (1–2), Stage 4: Skip Count by 2, 5, and 10 (Addressing)
 Target Numbers (1–5), Stage 7: Subtract Hundreds, Tens, or Ones (Supporting)
Print Formatted Materials
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Additional Resources
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