 Retrosheet
Digitizing playbyplay accounts of Major League Baseball games from the past century through the present. Freely download event files, which detail "literally every play" in big league baseball; game logs; schedules; narratives, which provide text playbyplay
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 Return of the Mathematical Tourist  Ivars Peterson (MathTrek)
In the newly published, updated edition of The Mathematical Tourist, Peterson writes, "...computers have become commonplace tools used by nearly all mathematicians, not only to communicate with each other but also to explore mathematical questions...
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 A Review of Logarithms (S.O.S. Mathematics)  Dept. of Mathematical Sciences, Univ. of Texas at El Paso
Since logarithms are exponents, the page presents a brief history of logarithms and reviews exponential functions before continuing on to logarithms and logarithmic functions.
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 The Review Zone  Tina Velgos
Indepth software reviews for parents and teachers. CDROM Reviews in all major educational topic categories including Math and Science; also an alphabetical CDROM index of all titles reviewed, each title with the recommended age or grade level.
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 Revision Universe  Arnav Rawat
Downloadable worksheets with questions on cumulative frequency; line graphs; mean, mode, median and range; pie charts; curved graphs; expanding brackets; graphical solution of equations; ratio; trial and improvement; area and perimeter; density, mass
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 Rhythms and Ratios  Peter Appelbaum
Rhythmic patterns are used to help the student act as apprentice mathematician and citizen mathematician (reading the newspaper, responsible consumerism, etc.). Rhythmic Ratios observations and introductions include the Basic Pattern Idea; Something to
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 Rice University School Mathematics Project (RUSMP)  Wells, Papakonstantinou; Rice University Center for Education
A project established to serve as a bridge between the Rice University mathematics research community and Houston area mathematics teachers. It sponsors a variety of professional development workshops, fosters reform efforts, encourages the effective
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 Rich Maths Tasks to Engage  East Midlands Maths Network
These teachermade rich maths tasks in number, algebra, shape, and data handling emerged from a collaborative project run by Jon Stratford, Lead Practitioner for the Specialist Schools and Academies Trust (SSAT): arrangements, clock face, chocolate dilemma,
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 The Ri Christmas Lectures  The Royal Institution of Great Britain
Register to watch the demonstrationpacked, funfilled videos that have formed a part of the British Christmas tradition for generations: "The natural history of a sunbeam," by George Porter; "Mathematics into pictures," by Christopher Zeeman; "Crystals
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 Rich Starting Points for ALevel Core Mathematics  Jonny Griffiths
Download PDF task files of 40 openended investigative activities for the A Level Pure Mathematics classroom: basic algebra, coordinate geometry, polynomials, curve sketching, uncertainty and inequalities, indices and surds, sequences and series, differentiation,
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 Rick's Math Web  Rick Schauer
Math curriculum geared toward special education learners with math disabilities and for learners preparing for the State of Minnesota's 8th Grade Basic Skills Test, with over 4,000 practice problems and stepbystep solutions for learners prekindergarten
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 The Ridiculously Enhanced Pi Page  The Exploratorium, San Francisco, CA
Pi Day celebrations, Pi music, links, beads, and pie. A certified 98% contentfree page.
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 Riding on Square Wheels  Ivars Peterson (MathTrek)
A square wheel may be the ultimate flat tire. There's no way it can roll over a flat, smooth road without a sequence of jarring bumps. However, a square wheel can roll smoothly, keeping the axle moving in a straight line and at a constant velocity, if
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 The RightAngle Triangle Solver  Steve Ayers
Input two sides of a right triangle, or one of its sides and one of its angles, and this site calculates the remaining sidelengths and angles. Also, convert decimals and fractions, and imperial and metric units of measure. Requires JavaScript.
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 Right Brained Math  Brandon Price
"Searching for divergence and creativity in all that mathy stuff." Price teaches algebra, geometry, statistics, and robotics at Austin's Khabele School, an International Baccalaureate (IB) World School. His blog, which dates back to March, 2013, has
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 Rigol'Math: énigmes, problèmes et curiosités mathématiques  JeanMarc Deleuze
Le calcul de Pi; le Jeu de Nim; Convertisseur base 10 > base 2; Multiplier sur les doigts; Multiplication égyptienne; Le carré magique; TicTacToe; Coloriage; et beaucoup plus.
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 Rinus Roelofs
Geometric sculpture, animation, structures, and "rhinoceros" (knots) by Roelofs, who exhibited as part of the Escher Centennial celebrations. After studying Applied Mathematics at the Technical University of Enschede (Netherlands), Roelofs earned a degree
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 Rivendell Educational Archive  Leigh Denault
An educational archive of materials in botany, history, math, science, drama, literature, philosophy, and art. Math resources include mathematician biographies, a fractal image gallery, and a bibliography.
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 River Crossing (Math Exploration Quilt)  Rik Littlefield; Hanford School
You want to cross a river to reach a point exactly opposite where you are currently standing. Explore this problem stepbystep, encountering the following basic ideas: 1) Pythagorean theorem; 2) time = distance / speed; 3) distance = time * speed; 4)
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 Riverdeep  Mathematics  Riverdeep Interactive Learning Limited
Online resources for students, educators, and parents, that build on Riverdeep Interactive Learning's courseware and interactive simulations. Read about or demo Destination Math, a curriculum on CDROM in Basic Mathematics, PreAlgebra, and Algebra I
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 Road Sign Math  Jamie Thingelstad
"Driving + Math = Fun." A game to play on the road, identifying signs that suggest basic or advanced arithmetic, or that display constants, sequences, or primes. See digital photographs of actual street and highway signs that meet the "RSM" rules. Submit
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 Robert J. Lang Origami  Robert J. Lang
Lang has catalogued and diagrammed over 400 models, combining aspects of the Western school of mathematical origami design with the Eastern emphasis upon line and form. Read about origami mathematics, which mathematically describe the underlying laws
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 Robert Kaplinsky  Glenrock Consulting  Robert Kaplinsky
Lessons consist of "The Challenge(s)," "Question(s) To Ask," "Consider This," and alignments to Common Core State Standards (CCSS): "How Can We Water All Of The Grass?" and "How Much Money Should Dr. Evil Demand?" and "How Did They Make Ms. PacMan?"
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 Robo Compass
"Geometrical constructions made easy": type commands such as "draw segment AB between points A and B" and "construct an arc z with center O and radius which is length of segment y," then watch Robocompass draw the construction onscreen with its animated
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 Robotics: Sensing, Thinking, Acting  The Tech Museum of Innovation, San Jose, CA
An exibit designed to introduce the science behind the design and operation of robots. Features four exhibit areas: Universal Robots: History and Workings of Robotics; Machines and Man: Robotics and Ethics in the 21st Century; Robot Art: Four Bay Area
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 RockandRoll Bridge  Ivars Peterson (MathTrek)
Startling scenes of rippling pavement, featured in a classic film that captured the 1940 destruction of the Tacoma Narrows suspension bridge in Washington state, rank among the most dramatic and widely known images in science and engineering. This old
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 Rockin' the Standards
Musical recordings by a rock band led by a veteran elementary school teacher who takes the lyrics from common tunes and changes them to help kids remember what they've been taught in school. Each of the fourteen songs on the album "Rockin' the Standards
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 Rodney Carr's Home Page  Deakin University, Australia
Books and software on statistics and advanced spreadsheet design. Contact the author for passwords to access downloadable documents and executable Microsoft Excel workbooks such as XLStatistics, for statistical analysis of data; XLGenetics, for illustrating
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 The Role of Calculators in Math Education  Heidi Pomerantz, Bert Waits for USI/CPMSA
This PDF article outlines the benefits of calculator use in mathematics classrooms from kindergarten through the university level, describing how calculators, when used appropriately, can be a tool for learning mathematics. The document has six sections:
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 Roles of calculators in the classroom  Pedro Gómez and Bert Waits
The site contains the extended papers of the conferences presented in the Topic Group 18 of the International Congress of Mathematics Education held in Seville in July, 1996. Papers are presented both as web pages and as PDF files.
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 The Roles of Interest and Mathematical Beliefs in Preservice Teachers' Learning to Mentor Online [PDF]  Ray & Renninger
Paper presented as part of a symposium, American Educational Research Association, Chicago, IL. A study of preservice teachers working with the Math Forum's Online Mentoring Guide.
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 Rolling a Die Until Every Face Has Appeared (Math Chat)  Frank Morgan, MAA Online
How many times do you think you need to roll a normal die to be 90% sure that each of the six faces has appeared at least once? Why? Answer: It takes 23 rolls, as Al Zimmerman discovered in a computer experiment rolling 5000 dice until 90% of them had
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 Rolling and Learning® with trisquare dice  Creative Enterprises, Inc.
A book describing math games to be played with 14sided dice, suitable for grades K6 or 8. Order form available on the web.
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 Rolling with Reuleaux  Ivars Peterson (MathLand)
Why is the cover of a manhole round? The usual answer is that a circular lid, unlike a square or hexagonal cover, won't fall through the opening. The circle works because it has a constant width, defined as the distance between a pair of parallel lines
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 Rolocu: the Colour Twist Puzzle  Charles Edge
Use logic and planning to put the pieces into place so that all rows and columns have all the colours in them.
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 A Romance With Numbers  K. Venkatasubramanian
Biographical information and thoughts about Srinivasa Ramanujan, from The Hindu, December 24, 1993.
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 Roman Numeral Conversion  InnoVision Technologies
Enter the Arabic number you want to convert to Roman, as long as it's less than 4000.
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 Roman Numeral Date Conversion Guide  Christopher Handy
A guide to deciphering Roman numeral year dates as commonly found in both modern and early printed books, including a Java applet that accepts Roman numeral input in the range 14,999 and converts it to Arabic form. The page explains the basic principles
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 Roman Numerals 101  Oliver Lawrence
The Romans used only seven letters; the combination of a letter and its position could represent any number. They also used a line above the letter, so the numbering system actually represents our own very closely, with fourteen different symbols. The
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 Roman Numerals and Dates  Paul Lewis
An illustrated introduction to Roman numerals, including Roman dates and calendar conversion, history and uses, a page on The Great 1999 Question, and a quiz. Three conversion tables are provided: Numerical 11449; Numerical 14502100; and Alphabetical
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 Roman Numerals Defined  Jim Loy
A listing of some common Roman numerals and a short explanation of how they work.
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 Roman Numerals  Math Forum, Ask Dr. Math Common Question
A selection of answers to questions about Roman numerals, such as how they represented decimals and fractions; with memory aids for remembering what letter represents what value.
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 Roman Numerals  Math Forum, Ask Dr. Math FAQ
Basics: How do I read and write Roman numerals? What are the rules for subtracting letters? How do I write large numbers? Web resources: introductions, charts, calculators, and converters. Calculations: Did the Romans use fractions?
How can I use Roman
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 Ron Blond  Ron Blond
Circle geometry applets to explore inscribed and central angles, tangents and radii, and tangents and inscribed angles. Also, applets illustrating the quadratic function (completed square and the discriminant), transformations of the sine and cosine functions,
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 Rose and Twinkleberry's Guide to Building Your Own Puzzles Using LEGO Building Blocks  Doug Walker
Plans for making 32 classic puzzles using LEGO blocks.
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 Rosebush Math Line Puzzles  Math Forum
Three puzzles: 1) plant 7 rosebushes so that they form 6 straight lines with 3 rosebushes in each line. 2) plant 10 rosebushes in 5 straight lines with 4 bushes in each line. 3) plant 19 rosebushes in 9 straight lines with 5 bushes in each line. Questions,
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 Rounding a Decimal  NASA Lewis Learning Technologies Project
Round 12.5861 to the nearest hundredth. A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Rounding Down?  Jim Loy
This is an article about the difference between rounding and truncation, with some stories about the effects of rounding (or truncation) on computer programs.
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 Rounding Numbers  Math Forum, Ask Dr. Math FAQ
How do you round a number to the nearest tenth (10th), hundredth (100th), thousandth (1000th), etc.?
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 Rounding Seconds  NASA Lewis Learning Technologies Project
Erv ran the 110 meter high hurdles in 13.27 seconds. His teammate, Willie, ran the same race in 12.91 seconds. Rounded to the nearest tenth of a second, how much faster was Willie's time? A detailed answer is provided. From NASA's 9th Grade Math Proficiency
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