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How to Solve It

A New Aspect of Mathematical Method

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16 minutes read | Text | 9 key ideas
In a world brimming with complexities, G. Polya's timeless masterpiece, "How to Solve It," serves as a beacon of clarity and methodical thought. Written with a grace that bridges generations, this book distills the art of problem-solving into a toolkit for life. Polya, a luminary in mathematics, unveils strategies that transcend his discipline, offering anyone—from bridge builders to word puzzle enthusiasts—the means to untangle life's knottiest dilemmas. By guiding readers to strip away distractions and zero in on the essence of a problem, Polya empowers us to face challenges with confidence and precision. As relevant today as when first published in 1945, these insights promise to sharpen your mind and illuminate your path through everyday decisions and intellectual pursuits alike.

Categories

Nonfiction, Philosophy, Science, Education, Programming, Mathematics, Logic, Computer Science, Technical, Textbooks

Content Type

Book

Binding

Paperback

Year

2015

Publisher

Princeton University Press

Language

English

ASIN

069111966X

ISBN

069111966X

ISBN13

9780691119663

File Download

PDF | EPUB

How to Solve It Plot Summary

Introduction

When faced with a problem, how do we approach it? What mental processes lead us from confusion to clarity, from an impasse to a solution? These questions lie at the heart of human cognition and achievement. Problem-solving is not merely a mathematical skill but a fundamental life capability that determines our effectiveness in nearly every domain. This systematic approach to problem-solving introduces a coherent framework that transforms the seemingly mysterious art of solving problems into an accessible, learnable process. The approach outlines distinct phases of problem engagement, from understanding the problem to looking back at completed solutions. It reveals the cognitive operations that skilled problem-solvers instinctively perform and provides a structured method for developing this capacity in anyone willing to learn. By illuminating the heuristic principles and mental techniques that facilitate discovery, this framework offers both practical tools for immediate application and deeper insights into the nature of human reasoning itself.

Chapter 1: Understanding the Problem: Defining Unknowns, Data and Conditions

Understanding a problem is the critical first phase of solving it, yet it's often the step we rush through in our eagerness to find answers. This foundational stage requires pausing to clearly identify three essential elements: the unknown (what we're seeking), the data (what information we have), and the condition (how the unknown and data relate). The process begins with careful examination of what exactly is being asked. Rather than immediately attempting calculations or constructions, skilled problem-solvers first ensure they can restate the problem in their own words. They ask themselves: "What is the unknown? What are the data? What is the condition?" This mental clarification prevents wasted effort on solving misinterpreted problems. Drawing appropriate figures or introducing suitable notation often helps visualize relationships between elements. The understanding phase involves separating various parts of the condition and examining each component individually. For mathematical problems, this might mean identifying distinct equations or constraints. In everyday problems, it means breaking complex situations into manageable parts. Understanding deepens through active engagement—attempting to restate the problem differently, drawing connections to familiar situations, or testing whether the condition seems sufficient to determine the unknown. An essential aspect of understanding is recognizing when a problem might be impossible or ill-defined. Asking "Is it possible to satisfy the condition?" serves as an early reality check. If a triangle problem requires constructing a shape with two sides totaling less than the third side, understanding the impossibility prevents fruitless calculation attempts. Similarly, detecting redundant or contradictory conditions early saves considerable effort. The understanding phase concludes when the problem solver can visualize the whole problem landscape—seeing clearly what they're searching for, what tools they have available, and what constraints they must work within. Like a traveler who studies a map before beginning a journey, this preparation ensures that subsequent steps move in productive directions. When understanding is thorough, the path to solution often becomes surprisingly clear.

Chapter 2: Devising a Plan: Finding Connections Between Known and Unknown

Devising a plan represents the bridge between understanding a problem and implementing its solution. This crucial phase involves discovering the connection between data and unknown—identifying how to transform what we know into what we seek. Unlike the mechanical execution of algorithms, planning requires creativity, intuition, and strategic thinking. The planning process typically begins by seeking connections to previously solved problems. The question "Do you know a related problem?" activates our mental database of experiences. When we encounter a complex geometric construction, recalling a simpler but similar problem often provides a starting point. This connection-making leverages our natural cognitive tendency to understand new situations through the lens of familiar ones. The question "Could you restate the problem?" serves a similar purpose, potentially revealing a formulation that makes connections more apparent. A well-developed plan typically emerges through progressive refinement. We might first identify a broad approach (using coordinate geometry versus synthetic methods), then narrow to specific techniques (using distance formulas versus vector operations), and finally determine concrete steps. This progression often involves exploring multiple pathways before selecting the most promising one. When direct approaches seem blocked, indirect methods like working backward from the solution or examining special cases can stimulate breakthrough insights. The questions "Could you solve a part of the problem?" or "Could you introduce auxiliary elements?" guide this exploration. The effectiveness of planning depends largely on our ability to see problems from multiple perspectives. Sometimes the connection between data and unknown becomes visible only when we transform the problem through generalization, specialization, or analogy. A challenging problem about three-dimensional rotations might simplify when reframed as a question about two-dimensional reflections. This mental flexibility—approaching problems from different angles—is characteristic of skilled problem-solvers. Recognizing when we have a viable plan requires both logical assessment and intuitive judgment. A promising plan connects all relevant data to the unknown through a coherent sequence of operations. It satisfies the given conditions and addresses the specific question asked. Before proceeding to execution, it's valuable to mentally rehearse the plan, checking for potential obstacles and ensuring it leads to the desired outcome. When properly conceived, a plan provides a clear roadmap for the work ahead.

Chapter 3: Carrying Out the Plan: Implementing Solution Strategies

Carrying out the plan represents the phase where conceptual understanding transforms into concrete action. With a clear roadmap established during planning, this stage focuses on careful, systematic execution of each step in the solution strategy. While often considered the most straightforward phase, implementation requires precision, attention to detail, and disciplined thinking. The fundamental principle during implementation is verification—checking each step for correctness before proceeding. Unlike the creative leaps that characterize planning, execution demands methodical progression. Each mathematical operation, logical inference, or procedural step should be scrutinized: "Can you see clearly that this step is correct? Can you prove it?" This vigilance prevents small errors from propagating through the solution. In geometric problems, this might involve confirming that triangles are truly congruent; in algebraic contexts, verifying that equations have been properly transformed. The implementation phase requires balancing persistence with flexibility. While following the established plan provides structure, we must remain alert to unexpected complications or opportunities for simplification. If a calculation becomes unwieldy or a construction seems impossible to complete as planned, we might need to reconsider our approach. However, too much deviation risks losing sight of the original strategy. The skill lies in knowing when to persevere through difficult calculations and when to pause for recalibration. Effective implementation often involves strategic organization of work. When solving complex problems, distinguishing between major and minor steps helps maintain perspective. Addressing significant parts of the solution first provides scaffolding for detailed work later. Similarly, maintaining clear notation and documenting intermediate results prevents confusion, especially in multistep processes. This organizational discipline becomes particularly important when solving problems that require extended chains of reasoning. The implementation phase concludes when we've transformed our plan into a complete solution that directly addresses the original problem. The final result should clearly identify the unknown in terms of the given data, satisfying all conditions specified in the problem statement. Successful implementation delivers not just an answer but a convincing argument that the answer is correct. Like a builder who follows architectural plans to create a stable structure, the problem-solver who implements effectively produces a solution that stands up to scrutiny.

Chapter 4: Looking Back: Examining and Learning from Solutions

Looking back at a completed solution represents a frequently overlooked yet invaluable phase of problem-solving. This reflective examination transforms each problem from a one-time challenge into a source of lasting insight and skill development. Rather than simply checking correctness, looking back involves deeper analysis of both the solution and the thinking process that produced it. The examination begins with verification: "Can you check the result? Can you verify the argument?" These questions prompt us to test our solution against the original conditions and data. For numerical results, we might substitute our answer back into the original equations, check for dimensional consistency, or assess whether the magnitude seems reasonable given the context. For proofs, we review logical connections and ensure each step follows from established principles. This verification confirms not only that our answer is correct but also that our solution process was valid. Looking back encourages exploration of alternative approaches: "Can you derive the result differently?" This question pushes us beyond satisfaction with our first successful method. Perhaps a geometric problem solved through coordinate methods could also yield to a more elegant synthetic approach. Perhaps an algebraic solution could be streamlined through clever substitution. By seeking multiple solution paths, we develop flexibility in our thinking and deepen our understanding of the problem's structure. Often, these alternative approaches reveal connections between seemingly disparate mathematical concepts. The most powerful aspect of looking back is extracting generalizable insights: "Can you use the result, or the method, for some other problem?" This question transforms specific solutions into reusable tools. The technique used to find a cube's diagonal might apply to higher-dimensional objects. The substitution that simplified a complex equation might work in other contexts. By consciously identifying these transferable elements, we build our problem-solving repertoire for future challenges. We move from solving isolated problems to developing a coherent, interconnected mathematical understanding. Looking back also provides emotional closure and confidence. When we thoroughly examine a solution—understanding not just that it works but why it works—we experience deeper satisfaction than from merely obtaining an answer. This cultivates a growth mindset where each problem becomes an opportunity for development rather than merely a hurdle to overcome. Like a traveler who pauses at a summit to appreciate both the climb completed and the broader landscape, the problem-solver who looks back gains perspective that enriches all future mathematical journeys.

Chapter 5: Heuristic Principles: Tools for Problem-Solving Discovery

Heuristic principles are systematic discovery tools that guide us toward solutions when algorithmic approaches fail. Unlike fixed formulas that guarantee results, heuristics offer flexible strategies that increase our probability of finding creative pathways through complex problems. These principles function as mental levers that help us productively transform problems, recognize patterns, and generate promising directions for exploration. The foundation of heuristic thinking lies in mobilizing our knowledge effectively. When facing unfamiliar territory, questions like "Do you know a related problem?" or "Have you seen something similar before?" activate relevant experience. This mobilization process connects current challenges to our existing knowledge base. Consider a student struggling with a complex integration problem who recalls a simpler integration technique previously mastered. The heuristic principle doesn't automatically solve the problem, but it points toward promising mathematical terrain where solutions might be found. Heuristic principles often involve strategic problem transformation. Techniques like symmetry recognition, decomposition into simpler parts, or considering extreme cases convert difficult problems into more manageable forms. When tackling geometric optimization problems, examining special cases (like equilateral triangles or squares) frequently reveals patterns applicable to general cases. Similarly, introducing auxiliary elements—additional lines in geometric problems or substitution variables in equations—can bridge conceptual gaps between what we know and what we seek. The practical application of heuristics involves developing sensitivity to progress indicators. Experienced problem-solvers recognize signs that suggest they're moving toward a solution: simplifications in expressions, emerging symmetries, or connections to known results. These indicators provide emotional reinforcement and directional guidance. Like a hiker who recognizes trail markers, the problem-solver learns to detect and interpret evidence of progress, adjusting strategies accordingly. Heuristic principles gain power through deliberate practice and reflection. Each successful application reinforces neural pathways that make these strategies more accessible in future situations. The question "Can you use the method for some other problem?" encourages conscious transfer of heuristic techniques across domains. This intentional generalization transforms isolated problem-solving episodes into a coherent development of mathematical thinking capacity. With practice, heuristics become internalized approaches that function almost automatically, providing intuitive guidance through the most challenging mathematical landscapes.

Chapter 6: Working with Analogies and Generalizations

Working with analogies and generalizations transforms individual problems into gateways for broader mathematical understanding. These complementary techniques extend our problem-solving capacity beyond isolated cases, allowing us to leverage similarities between situations and apply insights across diverse contexts. Mastering these approaches substantially amplifies our ability to navigate complex mathematical terrain. Analogical thinking establishes bridges between similar mathematical structures. When encountering a challenging three-dimensional geometry problem, recognizing its resemblance to a familiar two-dimensional case provides immediate traction. The question "Do you know an analogous problem?" stimulates this comparative thinking. The power of analogy lies in its transfer potential—we can apply solution techniques from the familiar case to the unfamiliar one. For instance, methods for finding a triangle's center of gravity naturally extend to finding a tetrahedron's center. This cross-application often requires adaptation rather than direct replication, but the analogical connection provides a crucial starting point. Generalization involves identifying underlying patterns that extend beyond specific instances. When we notice that a formula works not just for squares but for all rectangles, or not just for specific equations but for entire classes of equations, we engage in generalization. This process frequently begins with observation of particular cases, followed by the question "What broader principle might apply here?" Effective generalization requires discerning which aspects of a problem are essential and which are incidental. A student who solves probability problems for fair dice might generalize to understand probability for any fair multi-sided object. The interplay between analogies and generalizations creates a virtuous cycle of understanding. Analogies often suggest possible generalizations by highlighting structural similarities across contexts. Conversely, generalizations help us recognize analogous situations by identifying shared abstract patterns. Together, they form a powerful framework for knowledge transfer. A student who understands the analogous relationship between derivatives and velocity might generalize this to recognize that derivatives represent rates of change across many domains. Practical application of these techniques involves deliberate cultivation of pattern recognition. Skilled problem-solvers actively look for similarities between current challenges and past experiences. They consciously extract general principles from specific solutions and test these principles against new cases. When studying mathematical theorems, they ask not just "Is this true?" but "Why is this true, and where else might similar reasoning apply?" This habit transforms each problem from an isolated challenge into a building block for mathematical intuition, creating an increasingly rich network of interconnected insights.

Chapter 7: Decomposing and Recombining Problem Elements

Decomposing and recombining problem elements constitutes a fundamental transformational approach to problem-solving. This powerful technique involves breaking complex problems into manageable components, analyzing these components separately, and then reassembling them in novel configurations that reveal solution pathways. Like a chemist who understands compounds by analyzing their constituent elements, the problem-solver gains insights through deliberate decomposition and creative recombination. The decomposition process begins with thoughtful analysis of the problem's structure. When facing a complex condition, we separate it into distinct parts and examine each individually. For geometric problems, this might mean identifying key relationships between figures or isolating specific constraints. In algebraic contexts, it could involve separating equations into simpler sub-equations. The question "Can you separate the various parts of the condition?" guides this analytical division. A complex optimization problem might decompose into understanding constraints, identifying the objective function, and determining variable relationships—each component becoming more tractable when considered independently. The complementary process of recombination involves synthesizing components in potentially novel arrangements. After understanding individual elements, we explore how they might connect differently to reveal solution paths. This recombination often involves introducing auxiliary elements or modified perspectives. For instance, decomposing a difficult geometric construction problem might reveal that combining certain simpler constructions yields the desired result. The recombination phase frequently generates the "aha moment" when previously disconnected elements suddenly form a coherent whole. The strategic application of this technique involves recognizing which decompositions will be most productive. Some problems naturally separate along obvious lines—like dividing a geometry problem into separate cases. Others require more creative partitioning—perhaps examining a function's behavior in different domains or considering a problem from multiple theoretical perspectives. The art lies in finding decompositions that simplify without losing essential relationships between components. Similarly, effective recombination requires maintaining awareness of the original problem while exploring new configurations of its elements. This technique demonstrates remarkable versatility across problem domains. In computational thinking, divide-and-conquer algorithms solve complex problems by recursively breaking them into smaller instances. In creative problem-solving, decomposition helps overcome fixation by encouraging examination of individual assumptions. Even in everyday situations, breaking overwhelming challenges into smaller, actionable tasks makes progress possible. Through regular practice with decomposition and recombination, problem-solvers develop a fundamental mental agility that transforms intimidating problems into accessible opportunities for discovery and insight.

Summary

The systematic approach to problem-solving presented here can be distilled into one profound insight: effective problem-solving is not merely about finding answers, but about developing a disciplined yet creative mental process that transforms obstacles into opportunities for discovery. By moving methodically through understanding, planning, execution, and reflection—while employing heuristic principles like analogy, generalization, and decomposition—we develop not just solutions to individual problems but a fundamental capacity for mathematical thinking. The significance of this approach extends far beyond mathematics. The mental habits it cultivates—careful analysis, strategic planning, methodical execution, and reflective learning—form the foundation of effective thinking in virtually every domain of human endeavor. Whether tackling scientific research, business challenges, or personal decisions, these systematic problem-solving principles provide a framework for approaching complexity with confidence. In a world increasingly defined by novel problems requiring creative solutions, developing this structured approach to problem-solving may be among the most valuable intellectual skills we can cultivate—transforming not just how we solve problems, but how we understand and navigate reality itself.

Best Quote

“The first rule of style is to have something to say. The second rule of style is to control yourself when, by chance, you have two things to say; say first one, then the other, not both at the same time.” ― George Pólya, How to Solve It: A New Aspect of Mathematical Method

Review Summary

Strengths: The book provides a systematic and instructive overview of mathematical problem-solving guidelines that are natural, simple, and based on common sense. It is written in an instructive style that can benefit a wide audience, including mathematicians and those dealing with complex problems.\nWeaknesses: The review suggests that the book may not offer new insights to those already experienced in problem-solving. Additionally, the reviewer feels they read the book at the wrong time, implying a missed opportunity for greater impact.\nOverall Sentiment: Enthusiastic\nKey Takeaway: The book is a classic guide to problem-solving that categorizes approaches and methods effectively, making it a valuable resource for both mathematicians and individuals facing challenging problems, despite potentially lacking novelty for seasoned problem solvers.

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How to Solve It

By G. Pólya

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