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Developing Mathematical Reasoning
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Developing Mathematical Reasoning
The Strategies, Models, and Lessons to Teach the Big Ideas in Grades 3-5



March 2026 | 344 pages | Corwin

Math is not rote-memorizable. Math is not random-guessable. Math is figure-out-able.

Author Pamela Weber Harris argues that teaching real math—math that is free of distortions—will reach more students more effectively and result in deeper understanding and longer retention. This book is about teaching undistorted math using the kinds of mental reasoning that mathematicians do.

Memorization tricks and algorithms meant to make math “easier” are full of traps that sacrifice long-term student growth for short-lived gains. Students and teachers alike have been led to believe that they’ve learned more and more math as they move through the content, but in reality students are not necessarily progressing in their ability to reason mathematically.

Using tricks may make facts easier to memorize in isolation, but that very disconnect distorts the reality of math. The mountain of trivia piles up until students hit a breaking point. Humanity's most powerful system of understanding, organizing, and making an impact on the world becomes a soul-draining exercise in confusion, chaos, and lost opportunities.

In her landmark book Developing Mathematical Reasoning: Avoiding the Trap of Algorithms, Pam emphasized the importance of teaching students increasingly sophisticated mathematical reasoning and understanding underlying concepts rather than relying on set rules for solving problems. Now, this next companion volume, Developing Mathematical Reasoning: The Strategies, Models, and Lessons to Teach the Big Ideas in Grades 3–5, equips educators with practical tools to move beyond rote memorization toward true mathematical thinking for students in upper elementary grades. Focusing on additive and multiplicative reasoning, the book introduces strategies designed to improve mathematical reasoning, Problem Strings, and strategic modeling to strengthen student understanding.

Highlights include:

  • Reasoning-based strategies: Replace traditional algorithms with approaches that build critical thinking while ensuring understanding
  • Problem Strings: Step-by-step guidance on walking students through a sequence of problems that spark insight
  • Grade 3–5 focus: Comprehensive coverage of additive and multiplicative reasoning tailored for upper elementary learners
  • Practical tools: Ready-to-use routines, discussion prompts, and modeling techniques for immediate classroom application

Help students learn to think mathematically rather than memorize. Build confidence, deep understanding, and an appreciation for the logic and beauty of math.

 
Preface
About This Book

 
Language Use in This Book

 
 
Acknowledgments
 
About the Author
 
Part 1: Setting the Stage
 
Chapter 1: Mathematics for Teaching
What’s the Purpose of Learning Math?

 
The Development of Mathematical Reasoning

 
Spatial, Algebraic, and Statistical Reasoning

 
Major Strategies

 
Conclusion

 
Discussion Questions

 
 
Part II: Developing Additive Reasoning
 
Chapter 2: The Major Strategies for Addition
Additive Reasoning

 
Developing the Major Strategies for Addition

 
The Split by Place Value Strategy

 
The Add a Friendly Number Strategy

 
The Get to a Friendly Number Strategy

 
The Add a Friendly Number Over Strategy

 
The Give and Take Strategy

 
Comparing the Major Addition Strategies

 
Conclusion

 
Discussion Questions

 
 
Chapter 3: The Major Strategies for Subtraction
Developing the Major Strategies for Subtraction

 
The Remove by Place Value Strategy

 
The Remove a Friendly Number Strategy

 
The Remove to a Friendly Number Strategy

 
The Remove a Friendly Number Over Strategy

 
The Find the Distance/Difference Strategy

 
The Constant Difference Strategy

 
Comparing the Major Subtraction Strategies

 
Conclusion

 
Discussion Questions

 
 
Part III: Developing Multiplicative Reasoning
 
Chapter 4: The Major Strategies for Multiplication
Multiplicative Reasoning

 
Important Foundations

 
Developing the Major Strategies for Multiplication

 
The Smart Partial Products Strategy

 
The Smart Partial Products: Over Strategy

 
The Smart Partial Products: 5 Is Half of 10 Strategy

 
The Doubling/Halving Strategy

 
The Using Quarters and Scaling Strategy

 
The Flexible Factoring Strategy

 
Comparing the Major Multiplication Strategies

 
Conclusion

 
Discussion Questions

 
 
Chapter 5: The Major Strategies for Division
Important Foundations

 
Developing the Major Strategies for Division

 
The Smart Partial Quotients Strategy

 
The Smart Partial Quotients: Over Strategy

 
The Smart Partial Quotients: 5 Is Half of 10 Strategy

 
The Equivalent Ratios Strategy

 
Comparing the Major Division Strategies

 
Conclusion

 
Discussion Questions

 
 
Part IV: Putting It All Together
 
Chapter 6: Tasks to Develop Mathematical Reasoning
Sequencing Tasks

 
Problem Strings

 
Other Instructional Routines

 
Games

 
Hint Cards

 
Conclusion

 
Discussion Questions

 
 
Chapter 7: Modeling and Models
Strategies Versus Models

 
The Many Meanings of Model

 
Exploring Models by Their Best Uses

 
Our Modeling Framework

 
Conclusion

 
Discussion Questions

 
 
Chapter 8: Moving Forward
Mentor Mathematicians

 
Where to Start

 
Conclusion

 
Discussion Questions

 
 
References
 
Index

For educators seeking a clear and comprehensive understanding of the major strategies for teaching the four operations, this book is an invaluable
resource. It offers deep insights into numerical relationships and will strengthen both your mathematical understanding and instructional practice—and you’ll see these strategies in action through the included links and videos!

Laura Vizdos Tomas
School District of Palm Beach County
West Palm Beach, FL

Pam Harris has delivered a comprehensive resource for teachers to fully understand how to develop mathematical reasoning with their grade 3–5 students. This book equips teachers with knowledge about the major strategies students need to have for each operation with whole numbers, decimals, and fractions. It is the most thorough compilation of all the strategies needed for 3–5 students to truly build and develop their mathematical reasoning relationships and mental connections. After reading this book, you will be inspired to teach with the clear goal of empowering your students to do math like mathematicians and develop relationships and connections that build students’ mathematical reasoning
abilities.

Susan Smith
Lakota Local Schools
Liberty Township, OH

This book is for elementary teachers and anyone who wants to deepen their own understanding and help students truly learn. It empowers
teachers to make sense of the math for themselves so they can create classrooms where every child can make sense of it. Developing Mathematical Reasoning: The Strategies, Models, and Lessons to Teach the Big Ideas in Grades 3–5 will transform how teachers teach mathematics. Our students deserve to experience math in a way they can understand, it and this book will help
you achieve that!

Marria Carrington
Mount Holyoke College
South Hadley, MA

Pam Harris changed the way I think about math and the way I teach math. This book is the equivalent of her being in your classroom to coach you whenever you need it!

Patrice Tucker
St. Cecilia Catholic School
Houston, TX

Developing Mathematical Reasoning: The Strategies, Models, and Lessons to Teach the Big Ideas in Grades 3–5 is a practical and inspiring guide for teachers who want to center student thinking in math. As an instructional coach, I appreciate how it bridges research and everyday classroom practice. The strategies are clear, the examples are authentic, and the emphasis on reasoning speaks directly to what math educators are looking for.”

Melynee Naegele
Osage County Interlocal Cooperative
Claremore, OK

Pam Harris’s book is a must-have for teachers. It takes the guesswork out of what strategies to teach and how, offering clear examples and practical
guidance. With methods that spark curiosity and make computation meaningful, this resource will transform math classrooms into vibrant spaces for reasoning and problem solving.

Jennifer Lempp
Alexandria, VA

If you want to expand your mathematical content knowledge and gain confidence in your mathematical pedagogy, this book does both! Pam
Harris challenges readers to think deeply about mathematical concepts and approach problems with efficient strategies.

LaVon McLeod
Stark County Educational Service Center
Stark County, OH

I have been a math educator for over 30 years and always felt that something was missing in my style of teaching. I researched and tried
many new ideas over the years. This book’s idea of using strategies and mathematical reasoning with high dose patterning was my missing piece.
Since I have started strengthening my own number sense, I have now adopted this with all my students.

Tonya Beth Roberts
Henderson County Schools
Henderson, KY

Pam Harris has a gift for unpacking the various ways in which students can learn the fundamental skills of mathematics. Her focus is clear: help
students progress through various math concepts by using reasoning skills and conceptual understanding. I learned so much reading this book, and I’m confident you will too.

Liesl McConchie
Math With the Brain in Mind
San Diego, CA

If you’re a teacher who wants your students to be sense-makers, fluent and flexible thinkers, and empowered as learners of mathematics, then this is the book for you. Pam Harris has brought together important threads in mathematics education in a refreshingly rigorous and practical way: developing foundational mathematical skills, building connections and using logic, equipping teachers with practical tools, and supporting all students to effectively learn math—real math!

Michaela Epstein
Math Teacher Circles
Melbourne, Victoria, Australia

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