 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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 Ultra Fractal  Frederik Slijkerman
A Windows shareware program that creates images of fractals, allowing you to write your own fractal formulas, coloring algorithms, and geometric transformations in a simple formula language. A layering feature lets you combine different fractals and coloring
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 Ultra Fractal Gallery  Frederik Slijkerman
A gallery of fractal images created using Ultra Fractal, a Windows shareware program.
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 ULTRALAB  Anglia Polytechnic University, U.K.
A research centre that writes software for learners of all ages and researches all aspects of the use of technology in learning. Reports, papers, and articles; 'old' software and hardware computing archive.
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 UMass Lowell WebMathematica Scripts  Kenneth M. Levasseur, Department of Mathematical Sciences, University of Massachusetts Lowell
Download Mathematica scripts. Abstract Algebra: generate Cayley tables of EAAM groups, Zn, and the ring Zn; connect the dots to visualize finite cyclic groups; polynomial extensions; and a game on finding a morphism between two groups. Modeling: exponential
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 Una experiencia didáctica con CabriGeomètre: el seguimiento de trayectorias para manipuladores planos irredundantes  María José GonzálezLópez, Universidad de Cantabria,España
Una actividad geométrica consistente en realizar la simulación del movimiento de robots manipuladores planos con dos grados de libertad rotacionales y/o prismáticos, utilizando el entorno computacional CabriGéomètre.
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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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 Uncle Dan's Algebra Videos  Dan Suttin, Homespun for Homeschoolers
A set of 12 videos plus a CD containing 180page workbook and linebyline solution key. Samples and ordering information available on the site. Uncle Dan offers to email the 180page algebra workbook file as a free gift to anyone who emails him and
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 Uncle Kenny's Mathematics Pronunciation Guide  Kent Kromarek
Billed as a "megametamathematical guide for proper American English
pronunciation of terms and names, for the diacritally challenged," this guide
includes many mathematicians and mathematical terms encountered in high school
and the first two years
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 Uncorking Work Problems (SMILE)  David Drymiller, Marie Sklodowska Curie Metro High School
A lesson designed to teach students to solve problems about work using the formula work = rate x time; to solve equations containing rational expressions; and to strengthen basic skills learned in algebra. From the Practical and Applied Math section of
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 UNdata  United Nations Statistics Division
Search across the UN's statistical databases: education, human development, population, trade, gender, and more. Preview, download, and filter results by sources such as the State of the World's Children (SOWC) and Millennium Development Goals (MDG).
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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 Calculus  Faraz Hussain
An online book that introduces calculus through concepts and engineering applications. Read the illustrated chapters free online, or download the entire work as a PDF for a fee.
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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 Mathematics: From Counting to Calculus  Keith Kressin, K Squared Publishing, Inc.
A comprehensive book for anyone who desires clear and concise math explanations, written for a nontechnical audience to cover the math fundamentals normally taught from first grade through college (for more information, see the Table of Contents).
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 Understanding Projective Geometry (Question Corner and Discussion Area)  University of Toronto Mathematics Network
An indepth explanation of projective geometry in response to a high school student's question.
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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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 Undusting Napier's Bones  Alexandros Diploudis; HeriotWatt University, UK
Biographical information about the Scottish mathematician John Napier, generally considered the inventor of logarithms, with a Java simulation of Napier's bones, a method for performing arithmetic operations by the manipulation of rods (called "bones"
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 Une Balade dans le Monde des Polyèdres  Maurice Starck
Les polyèdres convexes, non convexes, et intéressants: les polyèdres uniformes, les stellations de l'icosaèdre, des tétraèdres remarquables, le découpage d'un tétraèdre par un plan, les deltaèdres
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 Unfair Dice  Ivars Peterson (MathTrek)
Dice represent an intriguing example of the interplay between randomness, chance, and physical law. The simplest mathematical model of a standard die is based on the assumption that the die is a perfect cube. A cube has six faces, and each face has an
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 Unfolding Orbifolds  Heidi Burgiel; The Geometry Center
A study of how a pattern can be reconstructed from an orbifold, using both handson exploration and the computer program TesselMania!. These activities are a good introduction to the movie Shape of Space. From Math 5337, Technology in the Geometry Classroom,
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 Unicursal curves and knot diagrams (Geometry and the Imagination)  Conway, Doyle, Gilman, Thurston; The Geometry Center
A unicursal curve in the plane is a curve that you get when you put down your pencil, and draw until you get back to the starting point. As you draw, your pencil mark can intersect itself, but you're not supposed to have any triple intersections. You
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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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 The Uniform Polyhedra  Roman Maeder
A shortened version of the notebook Polyhedra.ma from Illustrated Mathematics [Gloor/Amrhein/Maeder95]. Uniform polyhedra have regular faces and congruent vertices. Allowing for nonconvex faces and vertex figures, there are 75 such polyhedra, as well
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 Unit Conversion and Day of the Week  Stephen Phillips
Convert between units of distance, area, volume, mass, speed, temperature, pressure, energy, power, or force online, or find the day of the week for a given date. There is also a list of conversion factors for various units, including units of radiation,
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 UnitConversion.org
Perform online unit conversions for volume, distance, temperature, time, speed, and more for a total of 2,100 kinds of units in 78 different categories.
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 Unit Converter
The converter works for units of area, energy, pressure, volume,
temperature, mass, length, numbers, velocity etc. You put in a number and
select a base unit and select a unit to convert to. The conversion result
will immediately appear in the output
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 Uniteasy: Scientific Unit Conversion and Dictionary
The site contains a variety of unit converters, including for space and time (angle, area, length, time, velocity, volume, solid angle, and astronomical distance), electricity, acoustics, chemical, mechanics, magnetism, IT, heat/energy, light, and radiation.
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 The United States and the Metric System  Office of Information Services, National Institute of Standards and Technology (NIST)
A capsule history, with questions and answers, a metric chocolate chip cookie recipe, and some sample size relations (kilogram of butter to pound, etc.).
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 United States Historical Census Data Browser  Paul Bergen
A database on the people and the economy of the US for each state and county from 1790 to 1970. Data include historical census figures and general population characteristics such as "number of free white females," "number of free colored males," and "number
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 UnitJuggler: Online Unit Conversions  Pierre Di Marco
UnitJuggler offers free unit conversions, for distance and length, area, volume, weight and mass, temperature, time, and more.
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 UnitMath Example: Geometric Solids  Paul M. Price
Examples of how to use UnitMath with geometric solids: box (rectangular parallelepiped), cone (right circular), cylindrical solids (can  right circular cylinder; horizontal cylinder, partly filled), oblate spheroid, prolate spheroid, spherical solids
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 UnitMath  Paul M. Price
A calculation utility program for Mac or Windows, designed to answer questions written as equations made up of numbers, units (a unit is a quantity in terms of which the magnitudes of other quantities of the same type can be stated), precision, and operators.
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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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 The Units of Measure C++ Library  Keith Nicewarner
The purpose of this library is to try to make it more difficult to make
coding mistakes that incorrectly mix units of measure. This is done with a
set of C++ classes that provide typesafe manipulation of units of measure
for various properties.
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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 Universal Currency Converter  Xenon Laboratories Incorporated
An interactive currency table. Versions are available in English, Spanish, and Swedish. The Universal Currency Converter™ allows you to perform interactive foreign exchange rate conversion on the Internet. Type the amount of source currency in the input
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 Universal Math Solver  Stanislav Kublanovsky
Software that solves problems of arithmetic, algebra, trigonometry, calculus, and other mathematics. Graphs, tables, and automated verbal and written commentaries — also available in French, Russian, Dutch, German, Italian, Spanish, and Hebrew —
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 The University of Chicago School Mathematics Program (UCSMP)
A K12 curriculum begun in 1983, with educational materials designed to bring the real world into the classroom, emphasizing reading, problemsolving, everyday applications, and the use of calculators, computers, and other technologies. Unnecessary repetition
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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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 UniVirtual Slide Rule Emulator  Andrew Davie
A realtime, fully configurable, slide rule emulator in Java. Zoom, reconfigure onthefly, and work multiple slides and multiple cursors, each of which supports multiple gauge marks and hairlines.
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 Unizor  Zor Shekhtman
Whiteboard lectures for teenagers on algebra, trigonometry, vectors, matrices, combinatorics, probability, and statistics. Sign in for structured study, assignment functions, and more.
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 Unlocking Puzzling Polygons  Ivars Peterson  Science News Online
An ingenious proof settles a wickedly prickly question about unfurling crinkly polygons. Think of a polygon as a chain of rigid rods connected to each other in two dimensions with flexible joints. Start with any configuration, no matter how complex and
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 Unlocking Ways to Make Your Math Simple  Rajinder Goswami
An ebook meant to enhance calulating skills. It focuses on comprehension, speed, and accuracy. Two Flash examples provided; download the whole book for a fee.
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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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 Untangled  Mehta, Gayatri; Luo, Xiaozhong; et al.
Map and place logic blocks in this game to make more compact circuit layouts on a grid  and more efficient computer chips. Visually appealing graphs bring nodes closer to parents or children and untangle knots in graphs; behind the scenes, the accumulated
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 Untangling the Mathematics of Knots (MegaMath)  Nancy Casey; Los Alamos National Laboratory
Fundamentals of knot theory for a wide range of levels  a variety of activities for exploring knots made from pieces of rope. Students can make and verify observations about knots, classify them, combine them, and find ways to determine if two knots
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 US2020
By organizing a million mentors from industry, this organization hopes to provide "uplifting moments of discovery to children through realworld, handson projects and academic coaching" in science, technology, engineering and math (STEM) fields. The
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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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