Lesson 3

Count on or Count Back to Subtract

Lesson Purpose

The purpose of this lesson is for students to subtract within 1,000 using strategies that demonstrate an understanding of the relationship between addition and subtraction, including counting on and counting back.

Lesson Narrative

In previous units, students used counting on or counting back to subtract within 100. In this lesson, they analyze different methods, including counting on and counting back, to subtract within 1,000. They make connections between sums of 10 and sums of 100, for example $$5 + 5 = 10$$ and $$50 + 50 = 100$$. Students use the relationship between addition and subtraction as they find unknown values in subtraction and addition equations.
• Engagement
• MLR8

Learning Goals

Teacher Facing

• Subtract within 1,000 using an understanding of the relationship between addition and subtraction.

Student Facing

• Let’s find the difference between numbers.

Required Materials

Materials to Gather

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

What strategies are students using to subtract? How can you help students see the connections between addition and subtraction as they consider ways to subtract within 1,000?

Suggested Centers

• Five in a Row: Addition and Subtraction (1–2), Stage 6: Add within 100 with Composing (Supporting)
• How Close? (1–5), Stage 3: Add to 100 (Supporting)