 Prongo.com
Free online games, such as Batter's Up Baseball and Lemonade Larry, for practicing arithmetic, investing in the stock market with real time stock prices, using logic to guess a number and decipher secret codes, and more. Themes of other games include
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 A Proof of the Pythagorean Theorem by Liu Hui (third century A.D.)  Donald B. Wagner
Web version of an article which appeared in Historia mathematica, 1985, 12, pp. 713. Includes Chinese characters, which were not in the published version. Some statements here are no longer up to date, but the article has not been significantly modified.
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 A Proof of the Pythagorean Theorem  Isaac Reed
One of the most famous theorems in mathematics, the Pythagorean theorem has many proofs. Presented here is one that relies on Euclidean algebraic geometry and is thus beautifully simple.
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 Proof of the Pythagorean Theorem (Math Exploration Quilt)  Rik Littlefield; Hanford School
Proof by the scaling law.
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 Proof of the Pythagorean Theorem  Rik Blok
Pythagorean theorem: in a right triangle the square of the hypotenuse is equal to the sum of the squares of the sides containing the right angle. Two proofs: one by a construction, and one by the method of similar triangles.
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 Proofs in Mathematics  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
A discussion of the value of proofs in the classroom, followed by a collection of proofs classified as either simple or charming. Simple proofs: Number of vowels in a Lewis Carroll game; Pigeonhole Principle; Number of X's and O's; Coloring points in
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 A Proof that e is Irrational  Isaac Reed
A proof by contradiction that relies on the expression of e as a power series.
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 Proof: The Sum of Prime Twins is Divisible by 12  Mathematics Dept., College of Marin
Prime twins are prime numbers that are two numbers apart. For example 41 and 43 are prime twins. Can you PROVE that the sum of prime twins is divisible by 12?
(This proof doesn't work for the prime twins 3 and 5.)
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 Properties Glossary  Math Forum, Ask Dr. Math FAQ
What is an operation? What is an identity? What are the associative, commutative, and distributive properties? What is the property of closure? What is the inverse of something?
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 The Pros and Cons of Technology in the Classroom  Roy Pea, Larry Cuban, Bay Area School Reform Collaborative, TAPPED IN
Nationally recognized experts on the subject, Dr. Roy Pea and Dr. Larry Cuban offer their insights in this transcript of speeches each gave to a gathering of organizations that fund school reform projects. A transcript of questions and answers from the
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 Proudnerd.com  Heather Sable
"For the selfassured nerd": humorous tshirts, long sleeve tshirts, women's tshirts, sweatshirts, hooded sweatshirts, boxer shorts, hats and caps, bags and backpacks, mugs and cups, mousepads, apparel for kids, babies, and toddlers, and more. Solve
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 Providing HandsOn, MindsOn, and Authentic Learning Experiences in Mathematics (NCREL)  Cathy Cook; Pathways to School Improvement
A linked essay giving overview, background, and issues around constructivist theory and its implementation. "When educators begin to see learning as knowledge construction, they change their thinking about curriculum, instruction, and assessment, developing
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 Psychosemiotic Theory and Educational Practice  Alice Leonard
Walkerdine and Corran's (1979) paper showed how psychosemiology may account for developmental data as a potentially fruitful alternative to the better known stage theories, like that of Piaget. They argued that learning mathematics is an ideal activity
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 P.T. Chang
Articles by this math professor from the University of Alaska Anchorage's MatSu College include "The Ostentatious World of Algebra," "InService Training for the Math Teacher of the 21st Century," and "Retesting in a College Remedial Mathematics Course."
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 Ptolemy's Ptools  ThinkQuest 1998
Easytounderstand math projects for students to do by themselves or with adult direction. Triangle investigations of the perspectives of the 3D video games Star Fleet Academy, Quake II, and Sub Culture Submarine Adventure. "Quadrant projects" involve
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 Public Domain Materials  Mike Jones
A collection of public domain instructional and expository materials from a USborn math teacher who teaches in China. Microsoft Word and PDF downloads include a monthly circular consisting of short problems, "The BowandArrow Problem," and "Twinkle
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 Public Outreach, Education, Teaching and Reaching Youth (POETRY)  Sten Odenwald, National Aeronautics and Space Administration (NASA)
The goal of the IMAGE mission's education and public outreach program (POETRY) is to explain how solar storms affect the Earth, and to correct misconceptions about Earth's magnetic field, its radiation belts, and why we have aurora. Read the latest information
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 Public Understanding of Mathematics  Key Issues in Mathematics at the Math Forum
Links to organizations and articles that explore perceptions and assumptions nonmathematicians hold about mathematics and mathematicians.
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 Publishing or Programming? A Framework for the Development and Presentation of Work by Children on the World Wide Web  Judy Keiner
A paper to be presented at SIGGRAPH97, Los Angeles, August 8th 1997, involving process writing approaches, and including three criteria for evaluating Web pages. Also links to example sites.
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 PUERTRA  Javier Sánchez González
The software package PUERTRA implemented a theoretical study of formal properties of Islamic geometrical art. PUERTRA modeled the Islamic rectilinear interlaced lattices found extensively in wood work (artesonado ceilings, mosque minbars, doors and windows,
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 Pure Math Online
Pure Math Online uses live, personal tutors to help students with algebra and other math homework in real time over the Internet. Program information and signup for free demo are available on the site.
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 Pure Numbers Daily Blog
New equations every day, made of the individual numerals in the date. Daily entries in this blog, launched on 11 October, 2012 (10/11/12), preserve the order of the individual digits using arithmetic, geometry, trigonometry, combinations and permutations,
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 Purplemath  Your Algebra Resource  Elizabeth Stapel
Algebra modules provide lessons, practical tips, hints, worked examples, and point out common mistakes in basic triangle length (trigonometry) values, calculators (what model to buy), canceling units, domain and range, exponents, factoring quadratics,
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 Putting the Pieces Together (Making a Fractional Quilt) (SMILE)  Demetria E. McKnight, Bateman Elementary School
An lesson designed to motivate students to develop a sense of equivalent fractions; explore addition of fractions with unlike denominators; and learn to divide a whole number into specified equal parts. From the Arithmetic section of a collection of almost
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 Puzzle Choice
A wide choice of puzzles and games for all ages, including crosswords, wordsearches, brainteasers, number puzzles (a calculator is provided), logics, teacher resources and other online games, including mazes.
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 Puzzlemaker  Discovery Education
A puzzle generation tool for teachers, students and parents. Create and print customized puzzles, including math squares and number blocks, online, or buy a CD with editing tools and other extras.
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 Puzzle Page  The Black Stump Ltd.
More than 150 links to puzzle sites on the Web. A new site is added each week.
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 Puzzler  Franklin Institute Online
Puzzles from the inQuiry Almanack Puzzle Archive: e.g. Cryptograms, January, 1998. Coded messages hide famous quotations. A clue is offered to begin breaking the code, and an answer key is provided. One puzzle a month from March of 1995 through July of
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 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  Martin Watson
Blogs, comments, musings, design sketches, and photographs of mechanical puzzles by an avid collector and craftsman. Puzzle news, the author's own burrs (Watson's wormhole, digigrams, Dutch cubist), indepth explorations of manipulative puzzles (Puzzles
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 Puzzles of Leonid Mochalov  Leonid Mochalov
Numerical and visual puzzles, some in Russian only, most in English.
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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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 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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 Puzzle Up  Binary Arts Corporation
A collection of others' Java puzzles, baffler and logic questions, "for serious puzzlers," best of the week, and mazes and mysteries, each organized into the three different skill levels of young, brisk, and expert. Also, information on the company's
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 PuzzleUp  Emrehan Halici
New problems and games posted every week in a contest format. Register, read the competition's rules, and browse the archive of past problems.
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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 Workshop  maths online  University of Vienna, Austria
Make your own interactive "jigsaw," or multiple choice puzzles, to save and run on your own computer or to publish on the web. The Applet puzzle creation page requires Java; the Test puzzle creation page allows greater use of mathematical symbols.
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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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 Puzzlies.net  Michał Barciś
Play sudoku and griddler logic puzzles online. Log in to save game play and compete in the rankings.
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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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 Pyramid and Frustum Formulas (Ask Dr. Math FAQ)  Math Forum
Formulas for finding the surface area and volume of a pyramid and its frustum.
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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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 Pythagoras: Music and Space  J. BoydBrent
A brief introduction to Pythagoras' observations on the relation between music and number. Graphics show music intervals expressed as mathematical ratios. Pythagoras observed that when the blacksmith struck his anvil, different notes were produced according
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 Pythagoras' Theorem in Babylonian Mathematics  MacTutor Math History Archives
Linked essay examining four Babylonian tablets that all have some connection with the Pythagorean theorem. With references and other related web sites.
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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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 The Pythagorean Theorem and the Maya Long Count  Charles Wm. Johnson; Science in Ancient Artwork 
Various essays dealing with the possible extension of the Pythagorean Theorem to the third power in relation to the mathematical and geometrical appearance of the Maya long count fractals within progressive series of right triangles. It would appear that
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 Pythagorean Theorem  Bellevue Community College
A brief illustrated page describing the theorem, with a little historical background and a proof.
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