 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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 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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 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 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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 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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 U.S. Census Bureau
Information (searchable by keyword and browseable by subject) from summary data files across cities, towns, counties, states, and other geographic and demographic boundaries, useful for many purposes from allocating representation in legislative bodies
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 U.S. Department of Education
Extensive and varied education information in categories including: educational initiatives (President's and Secretary's priorities), funding opportunities, student financial assistance, research and statistics, news and events, programs and services,
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 Useless Facts about Pi  Paris
Facts "so useless not one of them has much bearing on pi's value": Euler's Relation; Irrationality (Niven's proof); Transcendence; Quadrature of the Circle with ruler and compass; The Content of nSpheres.
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 U.S. Energy Information Administration (EIA)
Links to facts/statistics on energy topics from A to Z: acid rain and air conditioning to world energy data on coal consumption, electricity prices, natural gas and oil consumption, and more. With tables, graphs, articles (some in PDF format), a Windows
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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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 U.S. Geological Survey  U.S. Department of the Interior
Scientific factfinding and research organization of the U.S. Dept. of the Interior; the principal source of scientific and technical expertise in the earth sciences within the U.S. Federal Government. Includes The Learning Web, where Teacher Developed
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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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 Using Manipulatives  Math Forum, Teacher2Teacher FAQ
Answers to a frequently asked question: What role can manipulatives play in the classroom?
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 Using Mathematica in the Mathematics Classroom  Univ. of Illinois
A course module designed for high school and lower division college mathematics teachers who are beginners with Mathematica and who want to learn to use this software package to create transparencies and handouts, computer demonstrations, and interactive
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 Using Sketchpad: Circles  Jim King, University of Washington
A sketch illustrating families of circles orthogonal to a given circle or line, which give some motivation for the idea of reflecting a point across a line or circle. Notes on Jim King's presentation at the Sketchpad User's Group Meeting in Cincinatti
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 Using Sketchpad: Conics  Peter Andrews, Eastern Illinois University
Two sketches illustrating techniques for constructing general conic sections, one on Isaac Newton's Organic Construction and one on the MacLaurin/Braikenridge construction of a general conic. Notes on Peter Andrews' presentation at the Sketchpad User's
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 Using Sketchpad in Calculus  Doris Schattschneider, Moravian College
Three sketches about parametric equations of curves and a sketch about a (then) unsolved problem about perpendicular bisectors of quadrilaterals. Notes on Doris Schattschneider's presentation at the Sketchpad User's Group Meeting in Cincinatti in January
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