Lesson 19
Solve Problems Involving Arrays
Lesson Purpose
The purpose of this lesson is for students to represent an array situation using an equation with a symbol for the unknown number and solve.
Lesson Narrative
In previous lessons, students represented multiplication situations using arrays and multiplication expressions with an emphasis on equal groups. Equal groups continue to be emphasized in this lesson as students learn that finding the product in a multiplication equation gives the total number of objects in the related array.
As students connect arrays to equations, they may write \(3\times5=15 \) or \(5\times3=15 \) to represent 3 rows of 5 chairs. This is fine as long as students can correctly describe where the “3 rows of 5 chairs” are in their array or equation. Keep collecting ideas that arise about commutativity.
 Action and Expression
 MLR8
Learning Goals
Teacher Facing
 Represent an array situation with an equation with a symbol for the unknown number.
 Solve multiplication problems involving arrays.
Student Facing
 Let’s solve problems involving arrays.
Required Preparation
Lesson Timeline
Warmup  10 min 
Activity 1  25 min 
Activity 2  10 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
Who has been sharing their ideas in class lately? Make a note of students whose ideas have not been shared and look for an opportunity for them to share their thinking in tomorrow’s lesson.
Suggested Centers
 Capture Squares (1–3), Stage 5: Multiply with 2, 5, and 10 (Addressing)
 Five in a Row: Multiplication (3–5), Stage 1: Factors 1–5 and 10 (Addressing)
Print Formatted Materials
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Additional Resources
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