Rectangular Arrays

Learning Resource Type

Learning Activity

Subject Area

Mathematics

Grade(s)

2

Overview

Students will construct arrays when given the number of rows and columns. The students will generate an equation to match their array model. This activity is designed to fit into the explain portion of a 5E formatted lesson plan.

This activity was created as a result of the ALEX Resource Development Summit.

Phase

During/Explore/Explain
Mathematics (2019) Grade(s): 2

MA19.2.4

Using concrete and pictorial representations and repeated addition, determine the total number of objects in a rectangular array with up to 5 rows and up to 5 columns.

UP:MA19.2.4

Vocabulary

  • Rectangular array
  • Rows
  • Columns

Knowledge

Students know:
  • how to use arrays and repeated addition as multiplication strategies.

Skills

Students are able to:
  • represent the total number of objects in a rectangular array as the sum of repeated addition.
  • choose and apply addition strategies to accurately compute sums for multiple addend problems.

Understanding

Students understand that:
  • repeated addition determines the total number of items in a rectangular array.

Learning Objectives

The student will create a rectangular array using concrete or virtual manipulatives given the number of rows and columns.

The student will draw a rectangular array given the number of rows and columns.

The student will describe a rectangular array using the numbers of rows and columns.

The student will write an equation to match the array model. 

Activity Details

  1. Open the Arrays slide show.
  2. Present the learning targets (Slide 2).
  3. Review vocabulary: array, row, column (Slide 3 & 4).
  4. Present pictures of rectangular arrays. Ask the students the following questions (Slide 5):
    How would you describe the rectangles?
    Is one of the arrays shaped like a square?
    Why do you think the array with 9 objects makes the shape of the square?
    If you want a long or wide rectangular array, should you have more rows or more columns?
    If you want a tall and skinny or narrow rectangular array, which should you have more rows or columns?
    If you want to create a square array, what should your rows and columns look like?

  5. Students will work with a partner to create rectangular arrays. Each partnership will share a set of dice and tiles. Each student should have their own paper to record their own arrays. The picture of the game directions is hyperlinked to the resource. The students will play this game for 15 minutes (Slide 6).
    Game: https://www.k-5mathteachingresources.com/support-files/roll-a-rectangular-array.pdf

  6. If color tiles are not available or learning is online, use virtual manipulatives (Slide 7).
  7. As students play, possible questions:
    How would you describe your array?
    How many rows do you have?
    How many columns do you have? 
    How many tiles do you have altogether? 
    How could this arrangement of tiles help you determine the total number of tiles you have without having to count every tile?
    How do you think arrays could help you count more efficiently?
    Do you have to have an even number of objects to make an array? Use the tiles to prove your argument.

  8. As the teacher observes students play the game, the teacher should take anecdotal notes or use a checklist.
  9. Display 3 pieces of student work. As you display each piece of student work, ask the students:
    What do you notice? What do you wonder?
    If students do not use appropriate terms such as an array, rows, and columns in their description, restate their response using the correct vocabulary.

Assessment Strategies

As the teacher observes students play the game, the teacher should take anecdotal notes or use a checklist. The teacher is looking to see if:

  • The student created an array with concrete or virtual manipulative when given the number of rows and columns.
  • The student drew a rectangular array when given the number of rows and columns.
  • The student described a rectangular array using the numbers of rows and columns.
  • The student wrote an equation to match my array model.



Variation Tips

The students may use concrete or virtual manipulatives.

If it is difficult for students to draw the arrays proportionally, the teacher or students may elect to use grid paper.

Background / Preparation

The teacher will need to print the checklist.

The teacher will want to practice using the virtual manipulatives listed to determine which is best for their students.

The teacher will need to prepare bags of color tiles and dice for each group.

Students will need paper and pencils.

 

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