Lesson 20

Lesson Purpose

The purpose of this lesson is for students to add and subtract within 1,000,000 with multiple compositions or decompositions.

Lesson Narrative

In this lesson, students use the standard algorithm for addition and subtraction to the hundred-thousands place. They build their fluency with the algorithm as they encounter examples where more than one digit has to be decomposed in order to subtract. Students also look at errors that are commonly made when using the algorithm to find sums and differences.
• Action and Expression
• MLR8

Activity 1: Add and Subtract Large Numbers

Learning Goals

Teacher Facing

• Add and subtract multi-digit numbers, with multiple compositions or decompositions, using the standard algorithm.

Student Facing

Let’s use the standard algorithm to add and subtract.

Required Materials

Materials to Gather

Lesson Timeline

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

Teacher Reflection Questions

What connections did students make between the decomposition of base-ten units using expanded form and using the standard algorithm when subtracting large numbers?

Suggested Centers

• Tic Tac Round (3–5), Stage 2: Any Place (Addressing)
• Number Puzzles: Addition and Subtraction (1–4), Stage 6: Beyond 1,000 (Addressing)