 Puzzlers  Bryan Clair, University of Chicago
A collection of Clair's favorite puzzles (no discussion or answers are provided): The Nine Dots; Weighing Coins; The Dollar Hotel, Planning an Orchard; The Math Department; Tea and Cream; Bugs on a Square; River Crossing; More Crawling Bugs; The Unexpected
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 Puzzles
A blog of math puzzles. Post your answers in the comments sections.
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Puzzles/Oneplayer Games  Jürg Nievergelt
Rubik's Cube and its variants. The 3*3*3* cube; Rubik's Revenge (4*4*4 cube); Pyramix (tetrahedron); Rubik's Clock; Rubik's Magic. Also Cryptequations, polyominoes, and links to a list of similar puzzles.
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 Puzzles, & Riddles  The Contest Center  Frank Rubin
Hundreds of puzzles and mathematical problems ranging from kindergarten through postdoctoral levels. For the easier puzzles, answers are provided on the site; names of those who submit correct solutions to harder problems are posted. See also Puzzles
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 The Puzzle TOAD  Tom Bohman, Oleg Pikhurko, Alan Frieze, and Danny Sleator, School of Computer Science, Carnegie Mellon University
Send the authors your solutions to their challenging graph theory, number theory, geometry, discrete mathematics, logic, and other puzzles. Revisit periodically to see the latest question, and download PDFs of solutions of past problems.
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 Puzzle Toons, The Citizen Scientist  Brian Mansfield
A comic strip devoted to puzzles, mind benders, and brain teasers. The subject matter of the puzzles ranges from mechanical devices and geometry to astrodynamics, chess, and billiards. Read back issues of Mansfield's column, dating to its inception in
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 Puzzle University  Amy Galitzer
A nonaccredited "university," created solely for fun. Everything is free to play and take part in. Register, pass a simple test, and advance from freshman to sophomore to junior to senior to grad student this way. The puzzles get harder as you progress.
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 PuzzleWise  Test Best International, Inc.
A supplemental program consisting of math crossword puzzles, each clue of which links directly to state and national gradelevel math skill expectations. The site offers samples, testimonials, prices, and a free newsletter.
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 Puzzle World  John Rausch
A searchable site with information and a discussion group (Puzzle Talk) about handcrafted mechanical puzzles. Most of the puzzles presented here are not the massproduced variety found in stores, but limited production puzzles produced by craftsmen (often
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 Puzzle Zapper  Alexandre Owen Muñiz
Original mathematical puzzles, some available in lasercut acrylic for sale: polyomino common superforms, pentomino coloring problems, miscellaneous polyomino explorations, flexible polyforms, square grid puzzles, visualizing sequences of numbers, Lissajous
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 Puzzling Lines  Ivars Peterson (MathTrek)
Sol LeWitt has often featured geometric and combinatorial themes in his sculptures, paintings, and drawings. In 1973 he composed "Straight Lines in Four Directions and All Their Possible Combinations," a grid of 15 squares, each inscribed with one or
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 Puzzling Primes  Isaac Reed
To fully comprehend our number system, mathematicians need to understand the properties of the prime numbers  but even finding them isn't so easy.
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 The Puzzling World of Barry R. Clarke  Barry R. Clarke
Brain teasers from Clarke's column in The Daily Telegraph (UK) and from his various puzzle books: liar problems, logic teasers, number conundrums, matchstick puzzles, lateral mindbenders, and more. With links to other puzzles sites and an article on
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 Pyramids and Algebra  David C. Miller
Four questions that explore the problem of creating a pyramid from a set of dominoes, dealing with the concepts of arithmetic series; derivation of square roots including a graphical method; scientific notation; exponential notation; quadratic equations;
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 Pythagoras' Haven  Jim Morey
Step through a geometrical Java applet proof of the Pythagoraean theorem  the square of the hypotenuse of a right triangle is equal to the sum of the squares of the other two sides.
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 Pythagorean Puzzle (SMILE)  Earl Zwicker, Illinois Institute of Technology
A lesson that models the phenomenological approach to enable students to prove the Pythagorean Theorem on their own using puzzle pieces and working together.
From the Geometry and Measurement and Algebra and Trigonometry sections of a collection of almost
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 Pythagorean Theorem (Manipula Math)  International Education Software (IES)
Java applets for experimenting with shifting, rotating, and moving pieces of quadrilaterals to prove the Pythagorean Theorem.
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 Pythagorean Theorem  Over 20 Proofs  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
A general exposition of the Pythagorean theorem, with proofs from Euclid to Garfield  and more. Also links to other sites on the Web with proofs.
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 Pythagorean Theorem  Warren F. Davis, Davis Associates, Inc.
An animated, nonmathematical, annotated proof of the Pythagorean Theorem, assumed to be the method of proof actually used by Pythagoras circa 550 BCE (see the Bronowski reference).
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 QPuzzle  XIAO Gang
A mathematical jigsaw puzzle: your goal is to recover a disordered photo by finding the inverse affine transformation. A French version is also available.
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 Quandaries and Queries (Math Central)  Dept. of Mathematics and Statistics, University of Regina, Saskatchewan, Canada
A math Question and Answer area for K12 students and teachers, with searchable archives of past questions and answers.
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 QuantumBrainBenders  Joel Klebanoff
A series of puzzles: find a series of numbers in a grid that add to the given sum. A new puzzle for each of three skill levels is posted daily. The site also includes an archive of previous puzzles.
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 The Quantum CyberTeaser  National Science Teachers Association (NSTA)
Archive of bimonthly problems posed online by Quantum, the math and science magazine. The magazine ceased publication with its July/August 2001 issue. Puzzles and most solutions are still available here.
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 The Quest for the Holy Value  Kjetil Valstadsve
Finding the correct value of pi. The likelihood of any random two integers having 1 as their greatest common divisor (no factors in common), has been proved to be 6 divided by pi squared  the numbers are prime in relation to each other. According to
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 Quia!  The Learning Group
Create your own Javaenabled quizzes, home pages, and learning games to play over the Internet: enter your material into a form, select a few options, and press a button. Games have been created and are available for browsing in mathematics, as well as:
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 Quick Trig Lessons  Matt Robinson
Brief lessons on ratios, triangles, identities, graphs, and formulas, with practice problems and a page of links to other math sites on the web.
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 Quiz Hub  Schmidel & Wojcik: Educational Web Weavers
A collection of online interactive learning quizzes that help K12 students enhance their core knowledge of English, languages, math, science, and social studies. Subscription required.
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 Quizma > Matemática Cálculo Robótica  Harold Suárez Guzmán
In Spanish: Clases y Orientación en Matemáticas Cálculo y Robótica. Fórmulas  Demostraciones  Ejercicios  Ejemplos  Cálculo Interactivo. Algebra, Logaritmos, Trigonometría, Geometría, Estadística, Ecuaciones, Problemas de Planteo, Funciones, Geometría
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 Quiz Me  D. Kell and Mercer County Community College
Interactive quizzes constructed using software provided by Addison Wesley Longman Publishers. Autoscoring, multiple choice selftests on whole numbers (place value, operations, applications, rounding, roots and order of operations); fractions (equivalencies,
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 QuizStar  Advanced Learning Technologies, Center for Research on Learning at The University of Kansas
Create online quizzes and organize the results. Features include the ability to attach multimedia files to questions, to make quizzes in multiple languages, and more.
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 QuizTree Math Games  Sierra Vista Software
A collection of online math quizzes in addition, subtraction, multiplication, and division.
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 Quizzes.cc
Use the menus and text boxes to create your own quizzes on addition, subtraction, multiplication, and division  or browse from among a selection. Click the appropriate button to reveal answers, grade responses, or generate new problems.
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 Radius and Diameter  NASA Lewis Learning Technologies Project
Mr. Jordan wants to put up a fence all the way across the middle of his round vegetable garden. If the radius of the garden is 3 feet, how many feet of fencing will Mr. Jordan need to buy? A detailed answer is provided. From NASA's 9th Grade Math Proficiency
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 Raise Smart Kids  Inna Shapiro
Download Powerpoint presentations of math problems, with answers: logic, basic arithmetic operations, natural numbers, pigeonhole principle, fractions, pouring, cutting, weighing, divisibility, and more. For Croatian translations of some of Shapiro's
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 Rama Math Help  Marty Schultz
Pages to help people solve the alien number machines in the Sierra game Rama, with a lesson in base 8 and 16 (and 10) and base conversions, useful for others, too. Includes a review of base 10 and an overview of bases 8 and 16. There is also a link to
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 Random (Blog)  Neil Bickford
Bickford writes "about mathematics, cellular automata, programming, Rube Goldberg Machines, and overall randomness." Posts of the selfdescribed "mathematician/programmer/scientist," dating back to May, 2009  when Bickford was 11 years old  have included
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 Ratio and Proportion  NASA Lewis Learning Technologies Project
If the ratio of boys to girls is 5 to 8 and there are 40 girls, which proportion should you use to find out the number of boys? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 The Real Y2K Problem (Math Chat)  Frank Morgan, MAA Online
Solution to the challenge: Every year in the millennium from 2000 to 2999 can be represented as the sum of consecutive integers, except one year. Which year cannot be represented as the sum of consecutive integers? New challenge: Where do you think you
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 Reason and Wonder  Michael Fenton
Blog by a Fresno (California) junior high and high school mathematics teacher. Posts, which date back to March, 2013, have included "Estimation 180 Rocks"; "Quadratics Matching Activity, Take 2"; "Solved the Student Engagement Problem Yet? Me Neither";
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 The rec.puzzles Archive  Massachusetts Institute of Technology (M.I.T.)
A list of puzzles, categorized by subject area, from the newsgroup rec.puzzles. Puzzles include solutions compiled from various sources, supposed to be definitive. Subjects include analysis, arithmetic, combinatorics, competition, decision, geometry,
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 rec.puzzles FAQs by Newsgroup  Dept. of Computer Science, Universiteit Utrecht
Information on the following topics: crosswords, analysis, arithmetic, combinatorics, competition, cryptology, decision, geometry, group, induction, Instructions, language, logic, physics, Pickover (Cliff), probability, reallife, references, series,
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 Recreational Mathematics  David Eppstein, Theory Group, ICS, UC Irvine
Some Web resources for recreational math, including links to Eppstein's pages own (Number Theory, Combinatorial Game Theory, and The Geometry Junkyard) and to pages by others.
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 Rectangle Perimeter and Side Length  NASA Lewis Learning Technologies Project
A rectangle with a perimeter of 24 inches might have adjacent sides measuring: 6 inches and 4 inches; 11 inches and 13 inches; 9 inches and 3 inches; or, 2 inches and 12 inches? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 A Recursive Process  Dan Anderson
Anderson's blog, which dates back to June of 2010, has included posts such as "Robocode & Math," "Standards Based Grading," "Cake:Frosting (A look into a proper ratio of real math:cool tech)," "Paper Towels WCYDWT (What Can You Do With This?)," "Two
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 Recursos de Matemáticas en Internet  Flavio P.
Información buscable, dividida en categorías que contienen enlaces comentados: altas, actividades, actualización, apuntes, buscadores, congresos, debate, enlaces, Escher, fractales, historia, lista general, Olimpiadas, publicaciones,
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 Recursos Gratuitos para Imprimir  Daniel Ajoy
Recursos para ayudar a los estudiantes en sus tareas escolares. (The long division worksheets include two versions of the method.)
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 Reflections in the Why  Chris Hunter
Blog by a K–12 numeracy helping teacher in Vancouver. Posts, which date back to September, 2010, have included "Linear Functions — Concretely, Pictorially, Symbolically"; "Math Manipulative of the Month — Base Ten Blocks"; "A Linear Functions
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 Reflections of a High School Math Teacher  Dave Sladkey
Blog by a teacher at Naperville (Illinois) Central High School. Posts, which date back to March, 2008, have included "Thinking Blocks," "School is a Place to Learn from your Mistakes," "More on When Students Teach," "Pop Goes the Weasel and the Quadratic
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 Reflections on Holes in Graphs and Reasoning  Zach Cresswell
Blog by a Michigan teacher of AP Calculus, Precalculus, and Algebra II who has taken graduate courses such as "Creativity in Teaching & Learning." Posts, which date back to May, 2013, have included "Trying a bit of '3 Act Math'"; "Multiple Methods for
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 Reform Calculus Resources  Harel Barzilai
Many printable activities and worksheets, some with solutions, longterm student projects, capsules and tutorials, and resources for instructors including a sample secondsemester calculus course with inclass groupwork activities, projects, and student
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