# 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)