# Contents

1. Section A: Add Within 1,000
1. Warm-up: Which One Doesn’t Belong: Numbers within 1,000
2. 1.1: Card Sort: Numbers in Their Different Forms
3. 1.2: Numbers in Different Forms Round Table
1. Warm-up: Notice and Wonder: Two Curious Tables
2. 2.1: Monuments and Falls
1. Warm-up: Number Talk: Hundreds, Tens, and Ones
3. 3.2: Two Ways to Add
1. Warm-up: Which One Doesn’t Belong: 247
2. 4.1: What is an Algorithm?
3. 4.2: Try an Algorithm
1. Warm-up: Notice and Wonder: Another Curious Table
2. 5.1: A New Addition Algorithm
3. 5.2: Compose New Units
1. Warm-up: Number Talk: Little More, Little Less
2. 6.1: Just Ones
3. 6.2: How Would You Add?
4. Section A Summary
5. Section A Practice Problems
2. Section B: Subtract Within 1,000
1. Warm-up: Number Talk: Subtract Two-Digit Numbers
2. 7.1: Strategies to Subtract
3. 7.2: Base-ten Drawings
1. Warm-up: Number Talk: Subtraction Strategies
2. 8.1: From Drawings to an Algorithm
3. 8.2: Card Sort: Diagrams and Algorithms
1. Warm-up: True or False: Does It Commute?
2. 9.1: Revise Subtraction Work
3. 9.2: Try the Algorithm
1. Warm-up: Notice and Wonder: Digits that Disappear
2. 10.1: A New Subtraction Algorithm
3. 10.2: Try Clare’s Algorithm
1. Warm-up: Number Talk: Subtract within 1,000
2. 11.1: Compare Two Subtraction Algorithms
3. 11.2: Use an Algorithm?
1. Warm-up: Number Talk: Threes
2. 12.1: How Would You Subtract?
3. 12.2: Greatest Difference, Smallest Difference
4. Section B Summary
5. Section B Practice Problems
3. Section C: Round Within 1,000
1. Warm-up: Estimation Exploration: Marching Band
2. 13.1: About 100? Close to 100?
3. 13.2: Close to Multiples of 100
1. Warm-up: Estimation Exploration: What Number Could this Be?
2. 14.1: Close to Multiples of 10
3. 14.2: The Nearest Multiples
1. 15.1: Can the Nearest Ten and Hundred be the Same?
2. 15.2: Round to Estimate
1. Warm-up: Number Talk: More Groups, Fewer Groups
2. 16.1: All the Numbers
3. 16.2: What’s My Mystery Number?
4. Section C Summary
5. Section C Practice Problems
4. Section D: Solve Two-Step Problems
1. Warm-up: True or False: Is it Greater?
2. 17.1: Quick Estimates
3. 17.2: Solve and Reason
1. Warm-up: Notice and Wonder: Diagrams
2. 18.1: Card Sort: Situations, Equations, and Diagrams
3. 18.2: Makes Sense to Me: A Gallery Walk
1. Warm-up: Notice and Wonder: The Unknown
3. 19.2: Represent, Solve, Explain
1. Warm-up: Number Talk: Two Steps
2. 20.1: Info Gap: Introduction
3. 20.2: Info Gap: Bake Sale
4. Section D Summary
1. Warm-up: Notice and Wonder: School Supplies List
2. 21.1: Make a Wish List
3. 21.2: What's on Your List?
4. Section D Practice Problems
5. Glossary