# Lesson 15

Estimate and Subtract

### Lesson Purpose

The purpose of this lesson is for students to estimate and find the value of subtraction expressions with decimals.

### Lesson Narrative

In a previous lesson, students found decimal differences in a way that made sense to them. In this lesson, students see that the standard algorithm for subtraction, which they have used in grade 4, also works for decimals. Students then estimate differences and find their values. Students are not required to use the standard algorithm, but see how it is an efficient way to subtract.

The lesson also includes an optional activity where students analyze an error in subtracting decimals with the standard algorithm. This activity can be used if students are still struggling with combining digits with the same place values in two numbers when they add and subtract.

Display the Decimal Subtraction chart from a previous lesson to be used during lesson synthesis.

• Action and Expression

### Learning Goals

Teacher Facing

• Subtract decimals to the hundredths using strategies based on place value and the relationship between addition and subtraction.

### Student Facing

• Let’s use place value to subtract decimals.

### Lesson Timeline

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

### Teacher Reflection Questions

What aspects of the math community are going well? What aspects would you like to work on? What actions can you take to improve those areas?