# Lesson 16

### Lesson Purpose

The purpose of this lesson is for students to add and subtract decimals.

### Lesson Narrative

In previous lessons students have found sums and differences of decimals using a variety of strategies. They have used place value reasoning, with words or equations, and have seen that the standard addition and subtraction algorithms also work just like they did for whole numbers as long as the same place values in the two numbers are added or subtracted. In this lesson, students add and subtract decimals with no method suggested. Students can use their favorite method or they can think strategically about the given numbers and adapt their strategy. The sums and differences encourage a variety of approaches such as adding on or adding or subtracting by place value.

The lesson also includes an optional activity where students find differences of more complex numbers and think strategically about which method to use. Whether they choose to use the standard algorithm or a different method using place value understanding, these problems help build fluency working with decimals.

• Action and Expression

### Learning Goals

Teacher Facing

• Add and subtract decimals to the hundredths using strategies based on place value.

### Student Facing

• Let’s use place value strategies to add and subtract decimals.

### Lesson Timeline

 Warm-up 10 min Activity 1 15 min Activity 2 10 min Activity 3 20 min Lesson Synthesis 10 min Cool-down 5 min

### Teacher Reflection Questions

What connections did students make between the different strategies shared? What questions did you ask to help make the connections more visible?