 Union of Bulgarian Mathematicians (UBM)
A voluntary, creative, nonpolitical organisation whose purpose is to bring together people who are interested in Mathematics and Computer science or are involved in activities related to those fields. Contact info, meetings.
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 Unique Online Math Flash Cards  Lambert Smith, MathRUS.com
Customizable formatting characterizes these flash cards for addition, subtraction, some multiplication and some division. Free 30day trial; afterwards, a subscription is paywhatyoucan. The author writes: "This website for online math flash cards differs
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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 Conversions, Unit Cancellation  Math Forum, Ask Dr. Math Common Question
A selection of answers to questions about unit conversions and cancellations, from "Convert: 3.25 cm to millimeters...." to "If you can run 100 meters in 10 seconds, how long, in days, hours, and minutes, does it take you to run 12,800,000 meters?"
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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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 Unit Converter
Key in units to convert. Available tabs include area, volume, time, density, length, temperature, moment of inertia, forces, distributed load, bending moment, and section modulus.
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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 for Ada  Dmitry A. Kazakov
Public domain software for dealing with physical measurement units. The library provides physically correct unit arithmetic and tools for input and output of units, which including support of various irregular units. As an illustrative example a platformindependent
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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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 UnitWiz
An online calculator converts units of length, area, density, energy, force, mass, power, pressure, speed, temperature, or volume.
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 Univalg  eGroups, Inc.
Mailing list for use by the Universal Algebra community: subscribe here, or browse archive by month. (Universal Algebra is a technical branch of mathematics related to algebra and model theory.)
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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 Framework for Science and Engineering  Part 5: Category theory  Petr Ivankov
Software for use in Category Theory. The web site describes its function and operation.
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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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 Universal Math Solver (UMS)  Severny Ochag International
UMS allows students to solve problems simply by entering them from any source, and provides a complete solution and presentation of the whole calculation process, accompanied by an audio commentary. See a screen shot or download a demo. Available in French,
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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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 Université de Montréal  Département d'informatique et de recherche opérationnelle
In French, with some pages available in English as well: Fondé en 1966, le DIRO fut le second département d’informatique créé au Canada. La recherche de pointe de son corps professoral, l’ampleur de son activité académique et son rayonnement international
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 University Departments  Canadian Mathematical Society (CAMEL)
An alphabetical list of Canadian university departments. Also links to
All U.S. Mathematics Departments online and
More Mathematics Departments in Universities around the World.
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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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 The University of Minnesota Calculus Initiative  The Geometry Center
Interactive technologybased modules for the engineering calculus sequence which emphasize geometric concepts of calculus while examining applications of mathematics to the physical and life sciences. Available are: the Rainbow Lab, Numerical Integration
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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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 Unsilence Students' Voices  Suzanne Alejandre
Article discussing how to provide an opportunity for all students to contribute to math classroom discussions. Originally published in the September, 2012, issue of the CMC ComMuniCator, journal of the California Mathematics Council, this article intersperses
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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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 Unstructured Grids (UG)  Institut für Computeranwendungen, UniversitU7auml;t Stuttgart
A flexible software tool for the numerical solution of partial differential equations on unstructured meshes in two and three space dimensions using multigrid methods. Its basic design is flexible enough to support many different discretization schemes.
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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 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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 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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 Use A Chair To Teach Math (SMILE)  Laura B. Reed, Rosa L. Parks School
A lesson designed to teach students some basic operations of math through measuring a chair. Sample questions: What size box would it take to mail the chair? Could two chairs fit in the same box? How many chairs could fit in this room? What area of space
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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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