# Lesson 21

Multipliquemos más decimales

### Lesson Purpose

The purpose of this lesson is for students to use place value understanding and multi-digit whole number products to find multi-digit decimal products.

### Lesson Narrative

In this lesson, students use place value understanding and properties of operations to find products of decimals. The numbers are more complex in this lesson so diagrams representing the products are less helpful. Students find the values of both types of expressions they have worked with in the last several lessons, products of two decimals to the tenth and products of a whole number and a decimal to the hundredth. Students find the products using a strategy of their choice. When they explain their reasoning, students will apply their understanding of place value to relate decimal products to whole number products based on the repeated reasoning they have acquired (MP3, MP7, MP8).

• Engagement
• MLR2

### Learning Goals

Teacher Facing

• Calculate products of decimals using whole number products and place value understanding.

### Student Facing

• Multipliquemos números decimales.

### 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

Reflect on a time your thinking changed about something in class recently. How will you alter your teaching practice to incorporate your new understanding?

### Suggested Centers

• Compare (1–5), Stage 4: Divide within 100 (Supporting)
• Compare (1–5), Stage 6: Add and Subtract Fractions (Supporting)