# Lesson 18

Represent Arrays with Expressions

### Lesson Purpose

The purpose of this lesson is for students to represent multiplication situations with arrays and multiplication expressions.

### Lesson Narrative

In a previous lesson, students arranged objects into arrays and described the arrays in terms of equal groups. In this lesson, students write expressions to represent arrays to further connect arrays and multiplication (MP2).

As students connect arrays to expressions, they may write \(3\times5\) or \(5\times3\) 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 expression. Keep collecting ideas that arise about commutativity.

- Representation

- MLR2

### Learning Goals

Teacher Facing

- Represent multiplication situations with arrays and multiplication expressions.

### Student Facing

- Let’s represent situations with arrays and expressions.

### Required Materials

Materials to Gather

### Required Preparation

Activity 1:

- Each group of 2 will need 20 connecting cubes or counters.

### CCSS Standards

Addressing

### Lesson Timeline

Warm-up | 10 min |

Activity 1 | 20 min |

Activity 2 | 15 min |

Lesson Synthesis | 10 min |

Cool-down | 5 min |

### Teacher Reflection Questions

In an upcoming lesson, students will learn about the commutative property of multiplication. What do you notice in their work from today’s lesson that you might leverage in that future 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)