 The TwoHeaded Quarter by Joseph Ganem  Chartley Publishing, LLC
A companion site to The TwoHeaded Quarter, written by a physicist scrutinizing daytoday financial decisions, such as "How far should you drive to buy cheaper gas?" and "Is money saved when you buy on sale?" and "How far should you drive to save money?"
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 Two Trains  Math Forum, a Classic Problem from the Ask Dr. Math FAQ
Two trains leave different cities heading toward each other at different speeds. When and where do they meet?
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 UC Berkeley Mathematics Department
Department info; a collection of the Berkeley [Ph.D.] preliminary exams; undergraduate study hints and survival guide; Notherian Ring (women in mathematics at Berkeley  includes WWW sites of interest to women mathematicians or grad students); Center
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 The Ultimate Online Review Book  ThinkQuest 1997
Previous New York State Regents Exams available to help you study for standardized tests. Tests and answer keys from the early 1990s are organized into Sequential Math 1, Sequential Math 2, Sequential Math 3.
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 The Ultimate Puzzle Site  van Gassel, Heijmans, van Veldhoven
A site in English and Dutch by three Dutch students. Contents include: Various Basic Puzzles and Riddles (no mathematics); Harder Puzzles and Riddles (no mathematics); Mathematical and Logicdeductional Puzzles with solutions; BrainTeasers; and Complex
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 Uncle Bob's Puzzles  Robert & Claire Mead, Haverhill, NH, USA
Math and logic problems (no solutions); if you have questions, want a hint, or want to submit a solution you're invited to email the author. Asterisks indicate greater difficulty: Blind Cowboy; A Game of Catch; The Next Three; Grandpa's Birthday; Square
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 Undergraduate Research Project in Random Tilings  Propp, Wilson
This project investigates different regions of random tilings of nxn squares with 1x2 dominoes: square, hexagon, fortress, dungeon, and Aztec diamond (the set of lattice squares completely inside a square tilted 45 degrees, discovering that the dominoes
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 underground mathematics  University of Cambridge
Free A level mathematics resources, mapped to "tube lines" reflecting big themes that run through maths "stations," and organized into categories such as rich examples, building blocks, fluency exercises, "many ways" problems, scaffolded tasks, "food
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 Understanding Algebra  James Brennan, Boise State University
In addition to "stuff to play with" on the web (a Graphing Applet (for exploring slope and intercepts of straight lines), a Prime Factorization Machine, a Prime Number List, a Quadratic Equation Solver, and a Quadratic Function Plotter), this book's full
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 Understanding Mathematics: A study guide  Peter Alfeld, University of Utah
A resource and source of encouragement, with questions and Alfeld's comments (Are you frustrated working through heaps of meaningless problems that are all alike? Does the thought "I can look it up if I have to" occur to you frequently? Do you feel that
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 Understanding 'Rate' Word Problems  Rick Garlikov
A conceptual explanation of doing various kinds of math "rate" problems (e.g., "distance/speed/time" problems, problems involving combining work done by different agents working at different rates of speed, quantity/proportion problems, etc.).
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 Understanding Temperatures  NASA Lewis Learning Technologies Project
These were the low temperatures recorded for January 15 in these cities: Minneapolis:  6 degrees; Cleveland: 5 degrees; Fargo: 11 degrees; Chicago: 2 degrees; Milwaukee: 3 degrees; Detroit: 1 degree. Which city had the low temperature closest to 0
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 UniformMotion Problems: Just Playing With Cars (SMILE)  David Drymiller, Morgan Park High School
A lesson that uses batteryoperated cars to teach students to solve uniform motion word problems using rate X time = distance; and gives them practice in measuring in the metric and English systems. From the Practical and Applied Math section of a collection
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 Unit Measurement Conversion  NASA Lewis Learning Technologies Project
Which statement is NOT correct? 96 cups = 6 gallons; 9 days = 216 hours; 84 ounces = 7 pounds; 2 miles = 10,560 feet. A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Units of Measurement  NASA Lewis Learning Technologies Project
Which object is matched with its appropriate unit of measurement? Milligrams for the weight of a textbook; Kilometers for the length of a sailboat; Grams for the weight of a needle; Kiloliters for the capacity of a reservoir. A detailed answer is provided.
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 The Universe of Discourse  Mark Dominus
Blog by the perl programmer who authored the book HigherOrder Perl and columns for The Perl Journal. Posts, which date back to November, 2005, have included "Fibonaccilike sequences," "More Liber Abaci," "The 3n+1 domain," "Biblical infallibility and
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 University of South Carolina High School Math Contests  David Sumner
Problems from the University of South Carolina (USC) High School Math Contests, since 1994. Walk step by step through illustrated solutions to each problem using the "next step" button. The delivery of questions is designed for competitive timing. Also,
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 Unlucky in Cards (Math Chat)  Frank Morgan, MAA Online
In his Contract Bridge syndicated column Phillip Alder says that the odds against getting a "Yarborough  a hand with no card higher than a nine" are 1827 to 1, and that the odds against two players getting a Yarborough on the same deal are about 182
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 Unsolved Problems in Function Theory  Alexandre Eremenko
Files available in PDF format: Some constants studied by Littlewood; Meromorphic functions satisfying certain differential equations (E. Hille); Does every universe contain a place where you can stay at rest? (Lee Rubel); Holomorphic curves with few inflection
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 Unsolved Problems in Number Theory, Logic, and Cryptography  Tim Roberts
This site "concentrates only on problems which are easily understandable to the amateur.... explainable on a single screen (perhaps 200 words), using simple terminology." Read brief descriptions of open problems such as the Chromatic Number, the Collatz
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 USA Map Jigsaw Puzzle  Jill Britton
Students are challenged to move each of the contiguous 48 states into the correct position on the map. Note the number of colors necessary for separation of the states.
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 USA Mathematical Talent Search (USAMTS)  The Art of Problem Solving Foundation
The USA Mathematical Talent Search (USAMTS) is a free mathematics competition open to all United States high school students that emphasizes problem solving and mathematical writing. Funded by the National Security Agency, USAMTS was initiated by George
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 USAMO/APMO/IMO/Putnam Archive  Kiran S. Kedlaya
Questions from some recent math competitions, in LaTeX or postscript format: the USA Mathematical Olympiad (USAMO) for high school students [19891999]; the Asian Pacific Mathematical Olympiad (APMO), a regional olympiad among countries on the Pacific
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 Usenet FAQ Archive : Recreation : Puzzles  Netmeg Internet
Problems and puzzles, with solutions, from the rec.puzzles archives, in the categories: analysis, arithmetic, combinatorics, competition, decision, geometry, group, induction, instructions, language, logic, physics, pickover, probability, real life, references,
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 Using Algebra and Discrete Mathematics to Investigate Population Changes in a Trout Pond (iMath Investigations)  Illuminations; National Council of Teachers of Mathematics (NCTM)
An online, interactive, multimedia math investigation that illustrates the use of iteration, recursion, and algebra to model and analyze a changing fish population. Graphs, equations, tables, and technological tools are used to investigate the effect
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 USolvIT  Paul Igodt and Frank De Clerck
In Dutch or English: USolvIT is a database containing thousands of mathematics/physics/statistics problems as an assessment tool. Part of the content is freely accessible via the web. A major part is for use by teachers in course contexts.
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 The U.S. Shirts Problem (PUMP Algebra Project)  Bill Hadley
When PATEOH Furniture Inc. went out of business, you were able to get another job at U. S. Shirts, a custom Tee shirt shop that prints shirts for customers. You job is to calculate costs for the various orders. For each order, U.S. Shirts charges $8
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 Utah Elementary Mathematics  David A. Smith
Blog of conceptual frameworks and other classroom resources for Utah educators implementing the Utah Core State Standards. Smith, the Elementary Mathematics Specialist at the Utah State Office of Education (USOE), has posted since October, 2013; and also
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 UVM High School Math Contest  Larry Kost, University of Vermont College of Engineering & Mathematics
Tests, with solutions, from contests dating back to the fortyfifth annual high school prize examination, of 2002. The tests consist of about forty questions encompassing number theory, algebra, and geometry. Also, lists of statewide and regional winners,
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 The Valuation Theory Home Page  FranzViktor Kuhlmann
A forum for all mathematicians who work in valuation theory or apply valuation theoretical results in their own field of research. The home page offers: information about conferences and special events; names and email addresses of mathematicians working
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 Vectors & Trigonometry  Dave Mason
Problems: Converting from Polar to Cartesian Coordinates; Adding Vectors; Hexagon Inscribed in a Circle; The Earth Curving Away From You; Surveying with a Protractor.
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 A View from the Back of the Envelope  Mitchell N. Charity
Pages about approximation. Counting by powers of ten includes the "what order of magnitude is ...?" game, illustrated instructions for counting to ten billion on your fingers, and lots of dots  a million dots on one page, and a dot for every second
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 Virtual Algebra Center  City College, CUNY
The home of the World Wide Algebra project. This international megaproject has several principal parts, including Algebraic Cryptography, The World of Groups, and The World of Polynomials. These include lists of open problems, conferences and seminars,
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 Virtual Laboratories in Probability and Statistics  Kyle Siegrist; Dept. of Mathematical Sciences, Univ. of AlabamaHuntsville
Interactive, Webbased modules for students and teachers of probability and statistics. Experiments are written in Java. Contents include: special models (Buffon's experiments, card experiments, Bernoulli trials, the ball and urn experiment, the matching
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 The Virtual Math Teacher  Russell Byer; AD Oliver Middle School, Brockport, NY
A reference site for middle school mathematics teachers, parents, and
students. The site provides monthly puzzles (and past puzzles, without solutions), suggestions for projects (real world math, math and economics, math and science, math and business,
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 Virtual Math Tutor
A new problem just about every day since October, 2010, with discussion and hints to follow.
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 Virtual Optima  Tony Hürlimann, Chris Hürlimann
A company offering consultancy, software (a linear programming language for mathematical optimization and modeling), and sport league schedules. It also offers a book of optimization problems, with sample problems available online.
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 Virtual Skies  NASA Ames Education Division
Tutorials, interactive illustrations, career explorations, decisionmaking scenarios, and selftests in each of the following areas: weather, aviation research, airport design, air traffic management, navigation, communication, and aeronautics. A "Teacher's
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 vismath  vismath GmbH
A shop of math manipulatives organized into "Build & Construct" (such as Fat Brain Toys, Itsphun, Papercraft, Pattern Blocks, PlusPlus, and Zometool); "See & Observe" (films, Mathematician's Dice, Playart magnetic sets, postcards, and wooden polyhedra);
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 Visual Fractions  Richard E. Rand
A site with 19 Java programs that provide instruction and practice in identifying, renaming, adding, subtracting, multiplying, and dividing fractions. Number lines are drawn to demonstrate each example. Programs include: Identify Fractions; Identify Mixed
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 VisuAlgo  Halim, Steven and Felix
"Visualizing data structures and algorithms through animation." Explore, watch electures, and solve problems on sorting, bitmask, linked lists, hash tables, binary heaps, binary search trees, graph structures, UnionFind DS, segment trees, Fenwick trees,
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 Visual Patterns  Fawn Nguyen
Visual patterns to extend and express algebraically, following the prompts on an accompanying handout. Nguyen, who teaches middle school math in California, has posted graphic arrays since December, 2012.
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 Vlaamse Wiskunde Olympiade  Flanders Mathematics Olympiad  Paul Igodt
In Dutch: the site contains more than 20 years of challenging math problems.
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 Vocabulary PuzzleMaker  Glencoe Online
Make the following types of puzzles to go along with your Glencoe text in prealgebra through geometry: crossword, word search with words, word search with clues, or jumble. Available for free download in both Windows and Macintosh formats.
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 Volume of Water in an Aquarium  NASA Lewis Learning Technologies Project
How much water will fit in an aquarium that is shaped like a box and is 10 inches high, 6 inches wide, and 14 inches long? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Vosenigmes.com  Kalimuse, LLC
In French: Vosenigmes.com permet de faire travailler ses cellules grises tout en s'amusant. Les petits comme les grands pourront se détendre tout en travaillant les mathématiques. Vosenigmes.com garde vos scores en mémoire, vous permettant de répérer
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 Waldomaths  Ron Barrow
Original applets on number, algebra and graphs; shape, space and measure; probability and data handling, including histograms; investigative tools (quadratic and cubic sequences); core (pure) mathematics; decision mathematics (network graphs and linear
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 WASL Math Prompts  Port Angeles School District, Washington state
Sample questions for the WASL, Washington State Assessment of Student Learning. Most questions have answers printed above the questions. Sample questions are offered for kindergarten through high school levels, organized by mathematical content, and accompanied
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 The Water Puzzle  Doug Ensley, Shippensburg University
Starting with a pail of water holding some unknown quantity greater than 8 quarts, and small (3 quarts) and large (5 quarts) vases as measuring devices, explore how to split 8 quarts of water from the pail equally between two people.
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 Water Puzzle  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
There are three glasses  3, 5, and 8 oz. The first two are empty, the last contains 8 oz of water. By pouring water from one glass to another make at least one of them contain exactly 4 oz of water. Investigation into this puzzle by experimentation,
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