 Dice and Valentine's Day Symmetries (Math Chat)  Frank Morgan; Christian Science Monitor
A dice challenge from S. H. Logue: The six faces of four dice have these numbers on them: A 1 1 5 5 5 5 B 4 4 4 4 4 4 C 3 3 3 3 7 7 D 2 2 2 6 6 6. You and your opponent each choose one die to use throughout the game. Each round you both roll, and the
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 Dictionary of Number Words  Intergalactic Power & Light
A dictionary of English language words, phrases, prefixes, suffixes, and
symbols that describe numbers. Cardinal Numbers, Ordinal Numbers, very large numbers, Noninteger Real Numbers, Numeric Ranges.
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 A Dictionary of Units  Cleave Books
A summary of units of measurement worldwide (current units and a few of historical interest); conversion factors to the SI (Systeme International); an outline of the SI; its basic defining standards and some of its derived units; all the SI prefixes
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 Didax Educational Resources
Didax publishes and distributes books, manipulatives, and software for math, reading, science, and art. The site offers free demo software, product descriptions, information requests, technical support, and current national educational standards. Didax
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 Did You Know? Applications of Statistics  Ian Gordon; University of Melbourne, Australia
Short stories about the application of statistics in different fields: Analysis of Gambling Strategies; Random surgical operations; TV phonein polls; Was it the orange juice?; Sunlight and skin cancer; Firefighters cause damage?!; What was the question
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 Digital Deletions  Pierre Ysewijn
An interactive JavaScript version of Conway's Digital Deletions game, in which numbers in a string are lowered to zero or erased. Users can play with different numbers of digits, different strategy levels, different starters, different sources of digits
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 Digital Generation Unit Conversions  Digital Generation
Choose from 26 different categories of engineering and scientific units. Also available at http://www.webcom.com/legacysy/convert2/convert2.html and http://www.legacysy.com/~legacysy/convert2/convert2.html.
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 DigitalLesson.com  Mark Tully
Website for middle school math teachers that has middle school math lessons, games, projects and activities for use in the classroom. Free newsletter, other resources for sale.
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 DigitalLesson.com: Middle School Math Downloads  Mark Tully
Free printable math games, a free PowerPoint Mathegories game, and a free newsletter for middle school math teachers five times per school year. DigitalLesson.com also offers downloads of middle school math lessons, projects, and games at reasonable
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 Digital Library: Science, Mathematics, Engineering and Technology Education (SMETE)  NEEDS
This site contains a searchable working prototype of a National Science, Mathematics, Engineering, and Technology Education Digital Library; a prototype federated search for the math community and the American Mathematics Metadata Task Force (AMMTF);
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 Digital Library  The Exploratorium, San Francisco
The Exploratorium AtoZ. Archived webcasts, web cams, past exhibitions: stills, movies, sounds, and other experimental items. Online versions of a few of the Exploratorium's interactive exhibits; the Exhibit CrossReference  an experimental database
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 Digital Mathematical Performance  Gadanidis, George; Borba, Marcelo; Hughes, Janette; et al.
Watch video, liveacted dramatic storyboards, and animations of how people "perform" mathematics: Flatland, "Help Me, Fermi," Should Parallel Lines Never Meet," "The Pleasure of Making 10" (linear equations), "The Waiter" (the missing dollar problem),
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 Digital Math  Santa Barbara County Education Office
A site to assist Algebra I, Grade 7, and Grade 6 students, their parents, and educators with the California State Mathematics Content Standards. Log in for Quicktime that provides stepbystep instruction to solve problems aligned with the mathematics
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 Digital Promise
Improving the opportunity to learn for all Americans, and accelerating innovation in education, through technology and research. Initiatives include Digital Promise Schools, in partnership with Verizon; the League of Innovative Schools; educator microcredentials,
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 The Digit Connection  Lizzie
A tribute to the number pi through music, poetry, and fiction. (Meet Sailor Pi!) Also includes a brief history of pi with some ways to calculate it, a quote collection, and ways to celebrate the number  even if it's not Pi Day.
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 Digits, Squares, and Cycles  Ivars Peterson (MathTrek)
Fascinating patterns lurk among the digits of whole numbers. Pick a positive integer, such as 57. Square each of the digits, then add the squares together: 5^2 + 7^2 = 25 + 49 = 74. Do the same thing with the digits of 74: 7^2 + 4^2 = 49 + 16 = 65. Keep
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 DIMACS  Rutgers & Princeton Universities, AT&T Bell Labs, BellCore
The Center for Discrete Mathematics and Theoretical Computer Science, an NSF Science and Technology Center. DIMACS is devoted to the development of the interrelated fields of discrete mathematics and theoretical computer science, among the most rapidly
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 Dimensions  Étienne Ghys et al.
"Mathematical vertigo guaranteed": this free, two hourlong film gradually takes viewers up to the fourth dimension. Available in many languages, and as a DVD.
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 DimensionU
Creators of educational software that put the action adventure fun of mainstream video games in a learning environment that prepares students for high stakes exams. First person shooter games Dimenxian, Evolver, and Meltdown contain 3dimensional virtual
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 Dipping math scores heat up debate over math teaching...  Bridget Murray, American Psychological Association (APA) Monitor
... psychologists differ over the merits of teaching children 'whole math'. An APA newsletter article that outlines the debate over the effectiveness of whole math, a demonstrative approach where manipulatives help children understand math concepts. "Some
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 Disabilities and Math Anxiety  Math Forum, Teacher2Teacher FAQ
Answers to a frequently asked question: How can I help my child who has a physical or learning disability?
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 Discoveries & Breakthroughs Inside Mathematics  American Mathematical Society (AMS)
Read articles and watch video news segments about the latest discoveries and applications of mathematics: "Do the Math Dance," "Mathematician Calms the Skies with Turbulence Detection Algorithm," "Become a Smarter Shopper," "The Science Behind Movie Magic,"
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 Discover Magazine  The Walt Disney Company
The monthly magazine of science and technology. Covers space, biology, health, medicine, AIDS, computers, new technology, the environment, astronomy, ancient life, archeology, evolution, physics, mathematics, ecology, and more. Available online: selected
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 Discover TI Neighborhood Workshops  Texas Instruments, Inc.
The free Discover TI Neighborhood Workshop provides a handson beginner's introduction to TI graphing technology. There will be 25 workshops throughout the United States. There is a choice of six different topics that appeal to middle school and high
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 discretemath  Math Forum
A discussion group for subject matter concerning teaching and researching of discrete mathematics at all levels. It began as a closed list for the researchers and educators who participated in the Rutgers University Discrete Math and Theoretical Computer
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 Discrete Math Problem of the Week (PoW)  Math Forum
Discrete math problems from a variety of sources, including textbooks, math contests, NCTM books, and puzzle books, and reallife situations, designed to reflect different levels of difficulty. From 1999 until 2002, this service challenged students with
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 Discussing Undergraduate Mathematics Education on the Internet  Steve Weimar for MAA Online; The Math Forum
Descriptions of good math discussion groups: what kinds of conversations you will find, how to access them, etc. Teaching and learning mathematics: MATHEDU, AMTE, MATHEDCC, DEVELOPMENTAL MATH. Topicspecific lists: MATHHISTORYLIST, APCALC, APSTAT,
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 Discussion Groups: Technology  Texas Instruments
Read, search, and post to groups about TI products: Scientific Calculators, TI10, TI73, TI80/81, TI82/83/83 Plus/Silver Edition, TI85/86, TI89/Voyage 200/TI92 Plus, CAS and Symbolic Math Guide, Graphing Calculator Comparisons, Derive, muLISP, TI
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 Discussion of Block Scheduling  Kidsphere K12 Mailing List
Dan Johnson, a teacher, describes block scheduling in his school: over 90% of faculty and students favored the new schedule. Discussion of some advantages and disadvantages.
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 Discussions  Math Forum
The Math Forum's discussions include mathematics and math educationrelated newsgroups, mailing lists, and Webbased discussions. Read recent and older messages, find out how to subscribe to a mailing list that interests you, read an MAA Online article
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 Disfruta Las Matemáticas  Rod Pierce, mathsisfun.com
Spanish language version of Maths is Fun.
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 DISME: The Art of Tenths  Simon Stevin
Definitions appertaining to Arithmeticall whole Numbers. Decimall arithmetike, Teaching how to performe all Computations whatsoeuer, by whole Numbers without Fractions, by the foure Principles of Common Arithmeticke: namely, Addition, Substraction, Multiplication,
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 Dissections: Plane & Fancy  Greg Frederickson, Cambridge University Press
A book that explores an area of mathematical recreations, called geometric dissections, or the cutting of one or more figures into pieces that can be rearranged to form other figures. With an emphasis on using as few pieces as possible, these geometrical
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 Distance Calculator Between Cities  Dan Gallagher
Enter two cities or countries and this CGI illustrates them on a scaled political map, calculates the distance between the two locations in miles and kilometers, and provides information about latitude, longitude, bearing, and airports. All latitude and
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 Distance, Rate, and Time  Math Forum, Ask Dr. Math FAQ
Distance = Rate x Time: A discussion and two problems.
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 Distance Recipe (Geometry and the Imagination)  Conway, Doyle, Gilman, Thurston; The Geometry Center
A technical definition of how to compute distance. Examples of distances; The Unit Disc Model; Passing from one model to another...
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 Divide!  Andrew Starr
A web page used to demonstrate that if you divide any two integers, eventually the decimals will repeat.
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 Dividing 12foot Boards  NASA Lewis Learning Technologies Project
Lewis needs 1,500 boards to build a small rocket. Each board must be 3 feet long. If boards are sold in 12 foot lengths, how many boards must Lewis buy and cut into 3 foot pieces to get the 1,500 he needs? A detailed answer is provided. From NASA's 9th
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 Dividing by 0  Math Forum, Ask Dr. Math FAQ
Why can't you divide by 0? Why is 0/0 "indeterminate" and 1/0 "undefined"? Why is dividing by zero "illegal"?
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 Dividing Decimals  NASA Lewis Learning Technologies Project
Dividing decimals: What is 12.8 divided by .04? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Dividing: Fractions and Mixed Numbers  NASA Lewis Learning Technologies Project
What is 1 1/2 divided by 1/2? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Dividing Fractions  Math Forum, Ask Dr. Math Common Question
A selection of answers to questions about dividing fractions, including an explanation of the "invertandmultiply" rule.
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 Dividing Fractions  Math Forum, Ask Dr. Math FAQ
How do you divide fractions? Say, 2/3 divided by 3/4.
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 Divisibility Rules  Calculation Tips & Tricks, The Math Forum
Tips for figuring out whether a number can be divided by the numbers 313, with a Spanish translation and an explanation of why the rules work by Robert L. Ward.
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 Divisibility Rules  Math Forum, Ask Dr. Math FAQ
How can you tell whether a number is divisible by another number (leaving no remainder) without actually doing the division? Why do 'divisibility rules' work?
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 Divisibility Rules to 50 and Beyond  Stephen D.T. Froggatt; Math Forum, Ask Dr. Math FAQ
A quick way of testing primality of larger numbers: the idea of deleting the last digit and adding or subtracting a multiple of the digit from the remaining number can be generalized to test for divisibility by prime numbers up to 50 and beyond.
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 Divisibility War  Diane Reed
A game designed for secondary level students studying basic mathematics to use the divisibility tests to determine whether a number is divisible by 2, 3, 4, 5, 6, 9, and 10.
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 Divisible by 3  Andrew Stadel
Stadel has taught prealgebra, algebra, and geometry in middle school since 2004. His blog about "interactions with math, logic, life, teaching, and the web they spin together" dates back to March, 2012, with posts such as "Survey your students"; "2012
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 Division by Zero  Dave Richeson
A blog about "math, puzzles, teaching, and academic technology." Posts, which date back to September of 2008 and sometimes introduce original applets, have included "Volumes of ndimensional balls," "Albrecht Dürer's ruler and compass constructions,"
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 Divisor Plot  Jeffrey Ventrella
"We hear of primes described as the 'building blocks' of all numbers. Let's turn that concept on [its] head. Instead, let's think of primes as the negative spaces behind complex objects. Imagine a series of picket fences stacked in front of each other.
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