2nd Grade Math Lesson

Zero Busters: Flexible Strategies for 3-Digit Subtraction

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2nd GradeBuilding Thinking ClassroomsCCSS.MATH.CONTENT.2.NBT.B.7, CCSS.MATH.CONTENT.2.NBT.B.950 min

Learning Objective

Students will flexibly apply place value decomposition, open number line, and constant difference strategies to solve 3-digit subtraction problems within $1, 000$ , including problems requiring regrouping across zeros.

Lesson Overview

Students explore three powerful subtraction strategies — Place Value Decomposition, Open Number Line Counting On, and Constant Difference — progressing from no-regrouping problems through regrouping across zeros, culminating in the anchored Constant Difference proof task.

Materials

Vertical whiteboards or large chart paper
Dry-erase markers (1 per group)
Erasers or paper towels
Random grouping cards
Student math journals (for consolidation notes)
Printed Four-Quadrant note-taking template

Scaffolded Task Progression

1Task 1

A submarine starts at

658

meters deep and rises

234

meters. How deep is it now? Solve using place value decomposition (break apart by hundreds, tens, and ones). Show your work on the whiteboard.

2Task 2

The submersible is at

742

meters and rises

218

meters. How deep is it now? Use place value decomposition. What happens in the ones place — do you need to regroup?

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