Lesson 10
Write Expressions and Equations to Represent Arrays
Lesson Purpose
The purpose of this lesson is for students to write equations to show the sum of the rows or columns of an array.
Lesson Narrative
In a previous lesson, students matched arrays to expressions with equal addends. In this lesson, students write equations with equal addends to represent an array as the sum of the number of objects in each row or the sum of the number of objects in each column.
- Action and Expression
- MLR2
Learning Goals
Teacher Facing
- Represent the number of objects in each column or in each row of an array using equal addend equations.
Student Facing
- Let’s write equations to represent arrays.
Required Materials
Materials to Gather
Required Preparation
Lesson Timeline
| Warm-up | 10 min |
| Activity 1 | 15 min |
| Activity 2 | 20 min |
| Lesson Synthesis | 10 min |
| Cool-down | 5 min |
Teacher Reflection Questions
What connections did students make between the structure of an array and the structure of the addition expressions they wrote? What questions did you ask to help make the connections more visible?
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)