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### Overview

This lesson presents a hands-on partner activity to introduce second graders to making rectangular arrays. Students will use number dice to roll numbers and then build the coordinating array. An equation will be written to show the sum of the equal addends.

This is a College- and Career-Ready Standards showcase lesson plan.

## 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.

### Primary Learning Objectives

The students will understand that equal addends can be arranged into rectangular arrays and can be used to find the sum. The students will build arrays using manipulatives and write an equation to express the sum.

### Procedures/Activities

Engage Students:

1. Show students the first three slides of the presentation with the pictures of the M&M's. Have them think-pair-share to discuss the following question: Which picture of M&M's is easier to count? Why? After sharing with their partner, invite students to share with the class. Introduce the term array. Explain that the second picture of M&M's forms an array. Make a list of some things that come in arrays (ex. eggs, donuts, canned drinks, bottled water, parking lots, etc.).

Procedure/Activity:

1. Students will look at the first slide with the cubes. Choose a student to arrange the cubes into an array. Ask: How did you arrange the cubes? After student explains, ask the class if they agree with his arrangement? Ask how many cubes there are altogether. Ask: How do you know? Did anyone get the total a different way?
2. Show the next slide. Ask a student to come show a different way to make an array with the same amount of cubes. Ask: Is the amount of cubes in both of these arrays the same? Discuss that no matter which arrangement the columns and rows are in you will still get the same sum.
3. Relate the array to addition. Say: Turn to your partner and talk about how we could write a number sentence to go with this array. Have students share. Model writing number sentences for arrays. Use the next two slides of the presentation for examples of number sentences.
4. Give pairs of students a grid (attached), a bag of 36 connecting cubes, and a pair of dice. Show slide with rules for the game "Roll an Array". One student will roll for columns and one student will roll for rows. They will work together to build an array and then write an equation to show the sum. Students will use the recording sheet (attached) to write the number sentences and record the numbers rolled. (Play for 15  -20 minutes)

Closing

1. After students have played the game, discuss the different arrays that were made. Have groups of pairs discuss their arrays together and look for similarities.
2. Give each individual student a blank piece of paper. Show the final slide and have students complete the task.

### Assessment Strategies

The teacher will question throughout the lesson using the following questions: Which picture is easier to count? Why? What are some things that come in arrays? Is there a different way to arrange the array? How many cubes are there altogether? How do you know?

The final task can be used for the teacher to assess the level of understanding of the student. A checklist is attached for the teacher to use to decide future activities based on individual student performance.

### Intervention

If a student could not complete the task, give him/her a lower number to build an array. Before having him try again, review the beginning of the slideshow with the student. Go back to the list of real world items that we see in arrays. See if the student can think of anymore on his/her own. Use the Internet to research products that come in arrays.

### Total Duration

31 to 60 Minutes

### Background/Preparation

A Smart notebook file is included for use with an interactive whiteboard. If you do not have access to an interactive whiteboard, it can be presented as a slideshow.

### Materials and Resources

Connecting cubes or counters, grid paper (attached), recording sheet (attached), slideshow presentation (attached)

### Technology Resources Needed

Interactive whiteboard or digital projector