 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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 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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 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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 pysimplex  Aaron Watters
Mixed Integer Linear programming modules: pysimplex provides some basic symbolic programming tools for constructing, solving and optimizing systems of linear equations and inequalities. It includes an implementation of the classical SIMPLEX linear optimization
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 Pythagoras Plays Ball  Ivars Peterson (MathLand)
Spring, baseball, statistics, math. In many ways, baseball is a numbers game: Strikeouts, home runs, batting averages, innings pitched, complete games, earned run averages, number of players left on base in scoring position in the bottom of the ninth
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 Pythagoras' Theorem: Elaboration on the Similarity Argument  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
Euclid included two proofs of the Pythagorean theorem in his Elements. A better known Proposition I.47 (Bride's chair) and VI.31 which is consistently overlooked in the introductory geometry courses. The latter,
however, renders the theorem virtually
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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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 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 Triples  H.B. Meyer
A Javascript calculator for pythagorean triples. In English and German.
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 Pythagoreisches Tripelprogramm  Heinz Becker
A Java applet that reads a and gives integer solutions of a^2+b^2 = c^2. In German and English.
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 Pythagoräische Tripel (Pythagorean Triplets)  H. B. Meyer
A calculator for Pythagorean triplets, making visible the oneto one correspondence between triplets and certain pairs of relatively prime numbers, and an interesting correspondence with certain sequences of letters A, B, or C. (Javascript is required.)
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 QAMA  QAMA, LLC
"The calculator that thinks only if you think, too," QAMA requires the operator to first enter a reasonable estimate. QAMA encourages rounding and rapid backoftheenvelope reckoning, but does not tolerate errors of magnitude or sign, or of basic operations
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 QA Quantum Algebra (Front for the Mathematics ArXiv)  Univ. of California, Davis
Quantum Algebra preprints, from the U.C. Davis front end for the xxx.lanl.gov ePrint archive, a major site for mathematics preprints that has incorporated many formerly independent specialist archives. Search by keyword or browse by topic.
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 Qhull  The Geometry Center
Download Qhull, software that computes convex hulls, Delaunay triangulations, halfspace intersections about a point, Voronoi diagrams, furthestsite Delaunay triangulations, and furthestsite Voronoi diagrams. It runs in 2d, 3d, 4d,
and higher dimensions.
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 QMG: mesh generation and related software  Stephen A. Vavasis; Computer Science Dept., Cornell University
The QMG package does finite element mesh generation in two and three dimensions. The package includes geometric modeling software, the mesh generator itself, and a finite element solver. It is free software whose source code is downloadable from the Web.
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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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 Quadralay's Cryptography Archive  Quadralay Corporation
Encryption standards, frequently asked questions (FAQs), and newsgroups. Clipper, Digital Telephony, History of Cryptology, Internet Security, Kerberos, PGP, RIPEM, and a glossary.
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 Quadrangle  Nikolay Khizhnjak
In Russian: Common properties of quadrangles, a cube and a circle are considered.
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 Quadratic Map  Ron Lee
The Quadratic Map is the chaotic dynamical system composed of the following equation: x_n+1 = 4 lambda x_n(1  x_n) with parameter lambda. The Java applet is a quadratic distribution plotter.
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 The Quadray Papers  Kirby Urner, 4D Solutions
An Introduction to Quadrays. The game of quadrays starts with a regular tetrahedron and four rays pointing from its center to the four corners; these or any ray built from these rays are labelled 4tuples  i.e. four numbers separated by commas and enclosed
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 The Quake Project  The Department of Civil and Environmental Engineering and the School of Computer Science at Carnegie Mellon University; and the University of Southern California's Southern California Earthquake Center (SCEC)
An NSF and DARPAfunded project developing the capability for predicting, by computer simulation, the ground motion of large basins during strong earthquakes, and using this capability to study the seismic response of the Greater Los Angeles Basin. Research
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 QuantFinanceJob.com
The quantitative finance community with tutorials, interview guides, questions and job searching resources for quants to land a successful financial engineering job on Wall Street.
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 QuantFinanceJobs.com
The job board for quantitative finance, financial engineering and risk management.
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 Quantitative Environmental Learning Project (QELP)  Greg Langkamp and Joe Hull, Seattle Central Community College
Supported by the NSF, QELP provides resources to integrate math and environmental science in college classrooms. It features data sets (search by
math or environment topic), a book of classroom exercises, and links to relevant Web sites. Each data set
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 Quantitative Reasoning  Bill Briggs; Dept. of Mathematics, Univ. of Colorado at Denver
Ideas and information about teaching Quantitative Reasoning courses (also called Mathematics for Liberal Arts Students), links to many Internet sites that support QR courses, and some information about a new QR book. Includes an article by William L.
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 Quantitative Reasoning for College Graduates: A Complement to the Standards  MAA Online
What quantitative literacy requirements should be established for all students who receive a bachelor's degree? Over the years, the Mathematical Association of America has approached this question in various ways, most recently by establishing, in 1989,
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 QuantSpot
A job search engine for quantitative finance, quant trading, financial engineering and risk management.
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 The Quantum Age Begins  MacTutor Math History Archives
Linked essay describing the beginnings of quantum theory, from Kirchoff's blackbody radiation work in 1859 to Bohr, Einstein, and von Neumann in the 1930's, with 33 references (books/articles).
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 Quantum Games  Ivars Peterson  Science News Online
Scientists studying quantum computation offer new perspectives on coin tossing, chess, and game theory. Theorists intend to apply the peculiarities of quantum behavior to game theory, two previously unrelated fields. These researchers propose that the
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 Quantum Information Page  John Aaron Smolin; UCLA Particle Beam Physics Laboratory (PBPL)
Papers on quantum computation, cryptography, etc.; quantum information on the Net.
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 Quantum Lie Algebras  Gustav Delius
A comprehensive, continuously updated bibliography of literature on Quantum Lie Algebras. Mathematica notebooks containing calculations and animations of quantum root systems are included.
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 QuantumQuick Queries  Ivars Peterson  Science News Online
Computer scientist Lov K. Grover of AT&T Bell Laboratories has found an an algorithm that relies on quantum mechanical principles that significantly speeds up the process of identifying a particular item in an unsorted list. Whereas the best possible
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 Quantum Theory  Dave Rusin; The Mathematical Atlas
A short article designed to provide an introduction to Quantum Theory, the study of solutions of the Schroedinger (differential) equation. Also includes a good deal of Lie group theory and quantum group theory, theory of distributions and topics from
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 Quasigroups (Catalogue of Algebraic Systems)  John Pedersen, W. Edwin Clark; Dept. of Mathematics, University of South Florida
Information about quasigroups from the Catalogue of Algebraic Systems. Definition, examples, decision problems, and links to related terms in the Catalogue.
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 QuasiTiler (Gallery of Interactive Geometry)  Eugenio Durand; The Geometry Center
Generate Penrose tilings or design your own nonperiodic tilings of the plane with this interactive application. In the process, you can select and visualize plane crosssections of a lattice in anywhere from 3 up to 13 dimensions. Geometry of Quasicrystals
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 QUdata.com  Icestone Trustee Limited
Online tools and reference library resources for data mining and knowledge discovery. Collection of free online statistical and scientific calculators, 2D and 3D function plotters.
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 Quelques feuilles de Maple  Maple expliqué en français  Canonne
An introduction to Maple in French. Algèbre Linéaire; Equations Différentielles; Equations et Inéquations; Fonctions; Géométrie; Graphiques; Polynômes et Fractions rationnelles; Programmation; Statistiques.
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 Query Interface to the Contents of the Mathematics Archives  University of Tennessee, Knoxville (UTK)
Search software, abstracts and reviews; teaching materials, etc. by keyword.
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 QueryTree  D4 Software Ltd
Drag and drop this free tool to explore, analyze, and visualize data — without special code, formulas, or even software: QueryTree queries tabular information within your web browser.
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 Qu'estce qu'un nombre? Edoc Mathématiques  Service du Film de Recherche Scientifique (SFRS)
Site basé sur le livre de S. Houzel, qui retrace l'histoire du nombre depuis l'Antiquité. In French. Site based on the book by S. Houzel, retracing the history numbers.
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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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 Questionnaire Design and Surveys Sampling  Prof. Hossein Arsham; University of Baltimore
Course notes on basic statistical analyses of data from sample surveys, especially for marketing science.
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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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