 What2Learn  John Rutherford
For free, a range of fun, interactive games and puzzles. Math topics covered include algebra, times tables, fractions, decimals, percentages, ratios and probability. Feebased service includes more activities, the option for teachers to add their own
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 What, How, and the Web  Cut the Knot!, Alexander Bogomolny
More on place value. "There is an obvious confusion there between two questions, what to teach and how to teach it. Does the failure of the New Math to present a specific topic necessarily imply that teaching this topic has no merit? The New Math has
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 What Is Your Answer to That Question?  Cut the Knot!, Alexander Bogomolny, with Don Greenwell
The question  Why study mathematics?  appears in a multitude of guises and a plethora of variants... Mathematics is often compared to art. Like literature, mathematics has metaphor, ambiguity, paradox, and mystery. It has history. Mathematics has contributed
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 What on Earth is a Logarithm?  Peter Alfeld, University of Utah
An understandingbased approach to powers and logarithms, with a link to a special example: how to convert a logarithm with respect to one base to a logarithm with respect to another base; and a Java applet logarithm calculator.
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 What's New  Terence Tao, UCLA
Updates on Tao's research and expository papers, discussion of open problems, and other mathsrelated topics. Blog posts, which date to February, 2007, have included "Riemannian manifolds and curvature" and "Sailing into the wind, or faster than the wind"
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 WhelkCome to Mathematics: Using Rational Functions to Investigate the Behavior of Northwestern Crows (iMath Investigations)  Illuminations; National Council of Teachers of Mathematics (NCTM)
An online, interactive, multimedia math investigation in which students use rational functions to explore the possible reasons behind the observation that northwestern crows consistently drop a type of mollusk called a whelk from a height of 5 meters.
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 Where to Start?  Cut the Knot!, Alexander Bogomolny
A discussion of math education: the intent of the NCTM Standards, reflections on the history of constructivism, classroom practices (with a link to Marilyn Burns' Math Solutions page), and a simple applet for solving linear equations. An interactive column
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 Which Polygon Sides are Parallel?  NASA Lewis Learning Technologies Project
Which of these line segments are parallel? Two adjacent sides of a triangle; Two adjacent sides of a pentagon; Two opposite sides of a rectangle; Two radii of a circle. A diagram and a detailed answer are provided. From NASA's 9th Grade Math Proficiency
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 Which Problem Equals 25 Percent?  NASA Lewis Learning Technologies Project
Which problem has an answer of 25 percent? 1) 10 is what percent of 50? 2) 25 is what percent of 75? 3) 25 is what percent of 125? 4) 20 is what percent of 80? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Why Not Geometry?  Cut the Knot!, Alexander Bogomolny
An exploration of the validity of teaching algebra at the middleschool level, testing, mathematics ewducation reform, the goal of education, and a suggestion that geometry might be a more important starting point.
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 Wikipedia Mathematics
The free encyclopedia's entries on mathematics. A wiki is a collection of interlinked web pages, any of which can be visited and edited by anyone at any time. Many pages also available in a range of foreign languages.
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 Wilson's Inversive Geometry with CabriJava  Wilson Stothers, University of Glasgow
An introduction to inversive geometry, with explanations and illustrations using
CabriJava. Many of the results and ideas are Greek, largely due to Apollonius of Perga. The approach is from the Klein viewpoint, using a group of transformations of a
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 Wired Math  Dean Murray, Soo Go, Jamie Pearson; University of Waterloo (Canada)
A free website created for students and teachers by a teacher for the University of Waterloo. The online games, drills, "follow up exercises," and answers
address topics common to middle grades on every continent. Also availalble from http://www.wiredmath.ca/
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 WisWeb  Freudenthal Institute
The Freudenthal Institute, a Dutch organization for secondary education, provides applets to support/extend the math instruction of students 12 years and older. For this site, WisWeb recommends versions 5 or higher of Internet Explorer, Netscape or Opera.
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 Wolfleg Tutoring  James R. Smith
Online tutoring in basic math, chemistry, and physics concepts.
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 Women's Adventures in Science  National Academy of Sciences
This project of the National Academy of Sciences showcases contemporary women in science, and highlights for young people the varied careers of some of today's most prominent scientists. The site draws from and accompanies Women's Adventures in Science,
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 Wondrous Worksheets  Wondrous Worksheets
Purchase a yearly subscription to view over 800 educational worksheets for children covering a variety of topics including maths, science, grammar, handwriting, comprehension and other things. Sample worksheets available free. Or make your own worksheets
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 Woodlands Math Zone  Woodlands Junior School, Kent, U.K.
Pages aimed at 711 year olds. Interactive games for math practice are organized under the following topics: Number Skills; Shape & Space Skills; Mental Maths; Preparing for Sats; Educational Games; Times Tables; Measures/Time; Worksheets; Understanding
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 Wordplay  John Langdon
On the application of ambigrams (words as art) in various fields of study. Most ambigrams are based on one form of symmetry or another; most of Langdon's ambigrams exemplify rotational symmetry.
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 Word problems that lead to simple linear equations.  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
An introduction to the mathematical representation of word problems, with a simple interactive exploration of linear equations.
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 Working with Fractions in Java  Michael Gilleland
Explores various highways and byways of fractions, such as continued
fractions, Egyptian fractions, and Farey sequences, with Java source code.
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 Working with Fractions Using Pattern Blocks  Margo Lynn Mankus
The objective of What's My Number? is to name the size of an object given the size of 1 unit. Materials include pattern blocks cutouts, a pattern block grid, a pattern block Java applet, and links to other pattern block activities elsewhere on the web.
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 Worksheet Genius  Simon Currigan
A free website full of printable worksheets, puzzles, and activities that can be differentiated and randomized at the touch of a button. Designed for those working with children at primary or elementary school.
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 Worksheet Works  WorksheetWorks.com
This site generates high quality PDFs of worksheets with the flick of a few checkboxes. Just specify level of difficulty, range of numbers, font size, or other parameters.
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 World Math Day  3P Learning
The World Math Day website provides five to eighteenyear olds with mental arithmetic questions to solve in competition with other math students from around the globe. Recent World Math Days, which take place in early March, have attracted participation
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 The World of Geometric Toy  Akira Nishihara
Play with animations and applets of Buckminster Fuller's Tensegrity and the Indian Ball (also known as the flexisphere), as well as wireframe renderings of the torus, the magic ring, the toroflux, the reversible polyhedron, and other objects. Nishihira
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 Worldometers.info
Counters that display the realtime data on world population (e.g., births this year, births today, deaths this year, deaths today, net population growth for today), government and economics (daily government expenditures toward health care, education,
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 WorldWideWeb for Operations Research and Management Science (WORMS)  Moshe Sniedovich; Dept. of Mathematics & Statistics, Univ. of Melbourne
A grassroots WWW site established by the Operations Research Group (ORG) at the Department of Mathematics, The University of Melbourne, Melbourne, Australia. WORMS' main objective is to complement the formal online activities of OR/MS Societies worldwide.
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 wrotniak.net  J. Andrzej Wrotniak
Includes shareware and freeware programs for Windows written by Wrotniak: scientific and regular calculators, a spherical geometry calculator, a logic and strategy game, a statistics graphing program, and a simple program to compute the area of a polygon.
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 www.multiplication.com  Krimsten Publishing
Ideas and products to help students understand multiplication and learn their multiplication facts. In Krimsten's rhyming method, for example, visualize a product such as 3 × 4 = 12 as a story about a tree ("three"), door ("four"), and elf ("twelve").
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 www.onlineklas.nl  Paul Koning
Flash games for practicing addition (sommenkampioen) or multiplication (tafelkampioen), with timers, high score tables, and memory components (tafels oefenen). Also, drill in identifying fractions, or converting between mixed numbers and improper fractions
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 WWW Resources for Teaching Statistics  Robin Lock; Mathematics Dept., St. Lawrence Univ., Canton, NY
A paper presented at Technology in Statistics Education, a 1998 conference for teachers sponsored by the Boston Chapter of the American Statistical Association. Its purpose is to direct readers to typical statistics instruction support sites on the WWW.
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 XGC: an eXtension of Goldbach's Conjecture  Andrea Ercolino
XGC is based on a new version of the Eratosthenes' Sieve. GC: Every natural n = 2*k, where k >= 3, is the sum of 2 odd primes. XGC(c,m): Every natural n = m*k, where k >= c + m, is the sum of m numbers belonging to the Euclid(c,m) set. Includes
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 XNumber World  James Redin
With the Extended Numerical Keyboards with Structured DataEntry Capability method, enter a number in the same way as you think on the number; for example, input one million and fiftyseven with the four keystrokes 1, million, 5, and 7, in that order.
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 XP Math  Tak L. Hui
Features include free materials designed to excite learners in mathematics and technology, a free eBooks
library, a collection of math sites, a database of mathematical careers, an interactive math games league and an active forum.
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 Yo Quiero Math  A Collection of Basic Math Tutorials  Lucila Rios
Tutorials (online videos and practice problems) for adult school students seeking to increase their understanding of basic high school Algebra to enter community college or pass the GED or CAHSEE.
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 You Have Found The Prisoners' Dilemma (Serendip: Playground)  Bryn Mawr College
Play a nonzerosum game where the best strategy for a given player is often one that increases the payoff to one's partner as well. The rules: on each turn of the game, you and your opponent must choose, without knowing the other's choice; following
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 Your Online Exchange to Additional Math Solutions  amaths.com
Tutoring, lessons, and tips for learning math; fun math topics; a marketplace for selling your used textbooks; and bulletin boards for discussion. Designed for students preparing for the GCE 'O' Level Additional Mathematics examination, based on the newly
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 Youth Accounts  FORUM Credit Union
Financial literacy games, stories, activities, articles, calculators, videos, and other resources  each set to a musical soundtrack  for learning about finance. Children aged 27 learn with Flip and Flop the frogs; eight to twelve yearolds, with
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 ZDNet University  ZiffDavis
ZiffDavis computer magazine publishers (PCWeek, MacUser, InternetUser, FamilyPC, etc.) sponsor online feebased computer classes and seminars taught on private moderated message boards. Most classes last 48 weeks, teachers have chat "office hours,"
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 Zona Land: Education in Physics and Mathematics  Edward A. Zobel
Text, Java, and VRML worlds demonstrating mathematical concepts in graphs, functions (including linear and polynomial), geometry, and trigonometry, as well as physics lessons on a similar model.
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 Zooba Island  Vrilliance Solutions
Free Flash games for children aged 7 to 12 which "inject fun and excitement into learning mathematics." Developed in consultation with Singapore's Ministry of Education Curriculum Planning Department around the Singapore mathematics curriculum, games
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 ZooWhiz  EdAlive
A curriculumlinked learning system for parents and teachers of children ages 515. Sample fun, colorful learning activities for math, word skills, and reading before registering a free "keeper" account or purchasing a premium "zoologist" subscription.
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 Z's Roguelike Stuff  Zeno Rogue
Mathematical games and projects include HyperRogue, a treasurecollecting, goblinkilling adventure set in nonEuclidean space  specifically, a hyperbolic plane of negative curvature filled with elixirs and slime beasts; and Hydra Slayer, which begins
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 Zunzun.com Online Data Modeling  James R. Phillips
Curve and surface fit 2D and 3D data online with a rich set of error histograms, error plots, curve plots, surface plots, and contour plots. The site also has a "Function Finder" to help determine the best equation to fit data.
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