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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 K-2



March 2025 | 320 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, but in reality their brains never get any stronger. Using these tricks may make facts easier to memorize in isolation, but that very disconnect distorts the reality of math.

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 a set rule for solving problems. Now, in this first companion volume, Developing Mathematical Reasoning: The Strategies, Models, and Lessons to Teach the Big Ideas in Grades K-2, she demonstrates how counting and additive strategies serve as the foundation for creating efficient, accurate, and flexible thinkers.

Everyone is capable of understanding and doing real math. This book:

  • Gives step-by-step guidance on how to teach the strategies, models, and big ideas that foster confidence and long-term success, preparing students for increasingly complex mathematical challenges
  • Offers the “what to do” to teach counting, addition, and subtraction in ways that promote reasoning over rote memorization
  • Provides practical tools such as problem strings, models, classroom routines, and discussion questions designed to implement reasoning-based practices
  • Includes supporting resources for creating a classroom culture where students see math as figure-out-able and gain confidence as mathematical thinkers

By addressing common misconceptions about math and providing practical strategies for teaching real math, this book shows that everyone can use the mathematical relationships they already know to reason about new relationships. In other words, everyone can math—even the very youngest students!

 
Preface
About This Book

 
Language Use in This Book

 
 
Acknowledgments
 
About the Author
 
PART I: SETTING THE STAGE
 
Chapter 1: MATHEMATICS FOR TEACHING
What’s the Purpose of Learning Math?

 
The Development of Mathematical Reasoning

 
Major Strategies

 
Conclusion

 
Discussion Questions

 
 
PART II: DEVELOPING COUNTING AND COUNTING STRATEGIES
 
Chapter 2: ALL ABOUT COUNTING
The Difference Between Counting and Counting Strategies

 
Foundations of Number

 
How to Develop Counting

 
The Number Sequence in the Teens

 
The Number Sequence After the Teens

 
Meaning of Decades

 
Student Interview

 
Conclusion

 
Discussion Questions

 
 
Chapter 3: COUNTING STRATEGIES
About Counting Strategies

 
Early Counting Strategies

 
The Counting On, Counting Back Strategy

 
Problem Types

 
Developing Counting Strategies

 
Conclusion

 
Discussion Questions

 
 
PART III: DEVELOPING ADDITIVE REASONING
 
Chapter 4: THE MAJOR STRATEGIES FOR ADDITION WITHIN 20
Additive Reasoning

 
Additive Strategies

 
Developing Addition Within 20

 
The Get to 10 Strategy

 
The Next Two Major Strategies

 
The Using Doubles to Add Strategy

 
The Add 10 and Adjust Strategy

 
Comparing the Single-Digit Addition Strategies

 
Conclusion

 
Discussion Questions

 
 
Chapter 5: THE MAJOR STRATEGIES FOR SUBTRACTION WITHIN 20
Developing Subtraction Within 20

 
The Remove to 10 Strategy

 
The Next Two Major Strategies

 
The Using Doubles to Subtract Strategy

 
The Remove 10 and Adjust Strategy

 
Finding the Distance/Difference Strategy

 
Comparing the Single-Digit Subtraction Strategies

 
Conclusion

 
Discussion Questions

 
 
Chapter 6: THE MAJOR STRATEGIES FOR DOUBLE-DIGIT ADDITION
Developing Multi-Digit Addition Strategies

 
The Splitting by Place Value Strategy

 
The Next Two Major Strategies

 
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 7: THE MAJOR STRATEGIES FOR MULTI-DIGIT SUBTRACTION
Developing Multi-Digit Subtraction Strategies

 
The Remove by Place Value Strategy

 
The Next Two Major Strategies

 
The Remove a Friendly Number Strategy

 
The Remove to a Friendly Number Strategy

 
The Remove a Friendly Number Over Strategy

 
Finding the Distance/Difference Strategy

 
The Constant Difference Strategy

 
Comparing the Major Strategies for Multi-Digit Subtraction

 
Conclusion

 
Discussion Questions

 
 
PART IV: PUTTING IT ALL TOGETHER
 
Chapter 8: TASKS TO DEVELOP MATHEMATICAL REASONING
Sequencing Tasks

 
Problem Strings

 
Other Instructional Routines

 
Games

 
Hint Cards

 
Conclusion

 
Discussion Questions

 
 
Chapter 9: MODELING AND MODELS
Strategies Versus Models

 
The Many Meanings of Model

 
Exploring Models by Their Best Uses

 
Our Modeling Framework

 
Conclusion

 
Discussion Questions

 
 
Chapter 10: MOVING FORWARD
Mentor Mathematicians

 
Where to Start

 
Conclusion

 
Discussion Questions

 
 
References
 
Index

Who better than Pam Harris to help you introduce K–2 students to mathematical reasoning—the language, the music, and the poetry of
mathematics. A must-read book filled with teaching strategies and creative ideas.

Jo Boaler
Stanford University
Stanford, CA

The abilities to count and to add are foundational to mathematics. All that follows is built upon these cornerstones. Get it right and math becomes
‘figure-out-able.’ In this book, Harris gives us the tools to get it right. Through real classroom examples, Harris takes us through strategies that
are easy to adopt and effective in getting and keeping students engaged in the work of understanding mathematics.

Peter Liljedahl
Simon Fraser University;
Vancouver, British Columbia, Canada

It is with great enthusiasm that I endorse this transformative book. At the heart of this work is a compelling discussion of reasoning. Through
rich narratives and classroom vignettes, we see that math fact fluency is not only figure-out-able but enjoyable—sparking curiosity and confidence
in every student. In short, this book is a masterclass in making math fact fluency meaningful and accessible for all.

Dr. Nicki Newton
Newton Education Solutions
Bridgeport, CT

This book is a gift to primary teachers. It offers clear ideas we can use right away to help students build real understanding and develop as
mathematical thinkers. From counting to additive reasoning, and through the power of models and Problem Strings, this book supports teachers in
making instruction more purposeful and responsive.

Graham Fletcher
Atlanta, GA

Finally, the book that K–2 educators have been waiting for is here! Harris wrote a book that explores the complexity of foundational numeracy skills and shares research-based approaches to develop mathematical reasoning with our youngest learners. This book will not only help
teachers cultivate curiosity and confidence and build a community of mathers, but it will also help teachers become the mathers they were
always meant to be.

Deborah Peart Crayton
My Mathematical Mind
Charlotte, NC

This book empowers K–2 teachers to deeply explore and understand the mathematics of the early grades, equipping them to foster
students’ mathematical reasoning and conceptual understanding. Grounded in research and filled with practical classroom examples,
it offers valuable guidance for transforming early elementary math instruction.

Marria Carrington
Mount Holyoke College
South Hadley, MA

What a powerful resource for equipping mathematics educators with the knowledge and skills necessary to develop their students’ mathematical
reasoning and promote their confidence as mathematicians!

Janet D. Nuzzie
Pasadena Independent School District
Pasadena, TX

If you’ve ever heard Pam Harris talk about the Levels of Sophistication in Mathematical Reasoning and thought, ‘I get it but what does that look like with MY students??’ This book delivers! It reveals how young children develop counting skills and thinking strategies for mathematical operations.
You’ll gain insights into student development, practical tasks to showcase their thinking, and modeling techniques that benefit every child in your classroom.

Christina Tondevold
Build Math Minds
Orofino, ID

Pam Harris offers teachers another invaluable resource for transitioning from repetitive procedural instruction to helping students develop deeper,
more conceptual understanding of mathematics. Through numerous examples of student thinking about mathematical concepts in the
K–2 classroom, she provides extensive treatment of the ways children approach problem solving. This comprehensive approach will certainly
prove helpful for teachers who are developing their understanding of how students learn to make sense of mathematics independently.

John Tapper
All Learners Network Inc.
Burlington, VT

This is a must-read for all K–2 teachers. Harris helps teachers understand how they can set their young learners up for long-term success in the math
classroom. This book provides teachers with a resource that combines content knowledge, high quality instructional practices and ready-made
instructional materials all in one! Upper elementary, middle school and even high school math teachers would all benefit from reading this book
and better understanding the development of mathematical reasoning, too.

Brandon Pelter
Bridgeport Public Schools
Norwalk, CT

For instructors

Please contact your Academic Consultant to check inspection copy availability for your course.

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ISBN: 9781071967546
£29.99