# Lesson 10

Multiply!

### Lesson Narrative

The purpose of this optional lesson is to provide students with practice multiplying rational numbers. Students see products of three numbers, and figure out what to do with a product of three negative numbers by grouping two of them together and multiplying those first. They see products involving unit fractions, reminding them that dividing by a whole number is the same as multiplying by its reciprocal. This will be useful in the next lesson when they start to divide rational numbers.

### Learning Goals

Teacher Facing

• Identify multiplication expressions that are equal, and justify (orally) that they are equal.
• Multiply rational numbers, including multiplication expressions with three factors, and explain (orally and in writing) the reasoning.

### Student Facing

Let’s get more practice multiplying signed numbers.

### Required Preparation

For the Card Sort: Matching Expressions activity, prepare 1 copy of the blackline master for each group of 2 students. If possible, copy each complete set on a different color of paper, so that a stray card can quickly be put back.

### Student Facing

• I can solve problems that involve multiplying rational numbers.

Building On