The purpose of this activity is to make connections between arranging objects to make an array and making a rectangle from equal-size squares. Students use the language of arrays to describe the rectangles they create (MP6) and learn that a rectangle composed of equal-size squares is an example of an array.

• Display student work.
• “Describe this rectangle.” (It has _____ rows of squares. It has _____ columns of squares. It has _____ squares in all.)
• If needed, ask:
  • “How many squares are in each row?”
  • “How many squares are in each column?”
  • “What equations could we write to represent the number of squares in this rectangle?”

The purpose of this activity is for students to finish partitioning a rectangle into equal-size squares. This work will prepare students for partitioning rectangles on their own in later lessons. In the Synthesis, students are invited to use what they know about the structure of arrays to anticipate how many equal-size squares will fill the rectangle without drawing any lines (MP8).

• Display the rectangle that has 4 squares in the first row, but is missing squares in each column (from the second problem).
• “How could you find the total number of squares that would fill this rectangle without drawing the lines?” (I can tell there will be 4 columns based on the top row. I can tell there will be 5 rows based on the first column, even though it is missing 1 square.)