 Radius and Diameter  NASA Lewis Learning Technologies Project
Mr. Jordan wants to put up a fence all the way across the middle of his round vegetable garden. If the radius of the garden is 3 feet, how many feet of fencing will Mr. Jordan need to buy? A detailed answer is provided. From NASA's 9th Grade Math Proficiency
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 Rainforest Maths  Jenny Eather
Flashbased interactive mathematics activities with an Australian rainforest theme, for grades K through 6. Topics include: Number & Number Systems; Operations & Calculations; Strategies & Processes; Patterns & Algebra; Measurement; Space & Geometry;
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 random.org  Mads Haahr
Generate random numbers on the Internet by using a web form (comparable to throwing dice), randomized sequences (lottery tickets), raw random bytes, virtual coin flips, or bitmaps. All numbers are tested statistically and the results available in realtime.
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 Random Walk Along a Line: A Simulation  David Sumner; University of South Carolina
A Javascript simulation of a particle moving along a straight line with absorbing states at either end. Modifiable variables: length of the line, starting position of the particle, number of trials. The theoretical expected length of a walk with these
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 RapidCalculator  ProAlgorithms.com
This mobile computing platform for web and handheld devices performs matrix operations like multiplication/inverses; plots graphs of functions and operations on polynomials; manipulates complex numbers; and evaluates other math, science, and engineering
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 Ratio and Proportion  NASA Lewis Learning Technologies Project
If the ratio of boys to girls is 5 to 8 and there are 40 girls, which proportion should you use to find out the number of boys? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Rational Number Tutorial  Joseph L. Zachary
A tutorial that explores the nature of rational numbers, the significance of the minimum and maximum integers in a rational number system, and the meaning of overflow. Includes a Java applet that opens in a separate window, for use alongside the tutorial.
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 Raw  DensityDesign Lab
The "missing link between spreadsheets and vector graphics," this open web app's interface lets you create custom vectorbased visualizations on top of the DataDriven Documents JavaScript (D3.js) library. Starting with delimiterseparated values in plaintext
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 Reasoning Mind  Reasoning Mind Inc.
Reasoning Mind is a nonprofit organization. It's also a core curriculum based on programs proven successful in Russia, China, and Singapore. A Reasoning Mind classroom combines a teacher and the computer, aiming to get kids so interested in math they'll
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 Rectangle Perimeter and Side Length  NASA Lewis Learning Technologies Project
A rectangle with a perimeter of 24 inches might have adjacent sides measuring: 6 inches and 4 inches; 11 inches and 13 inches; 9 inches and 3 inches; or, 2 inches and 12 inches? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Recursos de Matemáticas para 2º de Bachillerato y 1º de Carrera de Ciencias  Matemáticas de Bachiller
In Spanish: Libros que puedes hojear; videos que puedes ver introducción al Álgebra de lo Lineal, introducción al Cálculo Diferencial, introducción al Cálculo Integral, ejercicios de examen de Selectividad, Know How; Detector de Pardillos Matemáticos;
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 Regression Applet  R. Webster West, Dept. of Statistics, Univ. of South Carolina
An applet designed to teach students the effect of leverage points on a regression line. Students may add points to the plot by clicking the mouse button. By adding points far from the existing line, the regression line changes considerably. This is particularly
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 Regression Tools
Online, Flashbased regression tools for linear, logarithmic, exponential, power, polynomial, multiple linear, multiple polynomial, and nonlinear regression.
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 Relative Prime Applet (MSTE)  Nicholas Exner; University of Illinois at UrbanaChampaign (UIUC)
A Java applet that compairs pairs of numbers to see whether they are relatively prime. The main goal of this action is to demonstrate the theorem that the probability of two positive integers chosen at random being relatively prime is six divided by pi
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 Remote Interactive Optimization Testbed (RIOT)  Industrial Engineering and Operations Research, UC Berkeley
Interactive educational and research tools for optimization problems. Applications: Learn about practical applications of optimization technology to Major League baseball, openpit mining, computer network design, and modular parts fixturing. Experiment
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 Repeated Prisoner's Dilemma Applet  Mike Shor
A repeated prisoner's dilemma game in which the user plays for twentyfive
rounds against each of five different (unknown) 'personality types'. Demonstrates the value of cooperation and the ability to take advantage of
some simple rules.
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 Research Institute of Symbolic Computation (RISCLinz)
The Research Institute for Symbolic Computation, RISC, is an Austrian institute devoted to the field of symbolic computation. The site includes descriptions of various research areas, such as combinatorics, constraint solving, the theory of computation,
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 Research  Peter Alfeld; University of Utah
Researchrelated materials: An interactive applet that lets you explore the BernsteinBézier form of a bivariate polynomial; recent papers, complete bibliography, recent talks, computer graphics (illustrating various mathematical concepts: US Global Positioning
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 The RetroPsychoKinesis Project  Peter Moore and John Walker
Retropsychokinesis (RPK) is the claimed ability of certain subjects to alter random data generated, but not examined, prior to the time the data are presented to the subject. Read about or run bell curve, clock face, or pendulum feedback programs (Java
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 Rice Virtual Lab in Statistics  David M. Lane, Rice University
A comprehensive interactive resource for studying statistics, in four modules: HyperStat Onlinean introductorylevel hypertext statistics book, with links to other statistics resources on the Web; simulations/demonstrationsJava applets that display
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 RICHplot  Richard Davies
A Java applet for plotting userdefined trigonometric functions. Includes the following functions: sin, cos, tan, abs, sqrt ,+ , ,* ,/ ,^ (power function), asin, acos, atan, ln (log to the base e) and exp. Requires a Javaenabled browser.
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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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 Rincón Matemático Tests interactivos  Mario A. Bunge
Exámenes multiple choice de Precálculo, Matemática, Análisis Matemático y
Álgebra lineal. Cada examen se presenta en dos formatos: PDF y HTML.
El PDF se imprime y se utiliza como una hoja de examen. Realizada la
prueba, se recurre al HTML (quiz
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 RngPack  Paul Houle
A pseudorandom number generator package for Java. Pseudorandom means that the "random" numbers are generated by a deterministic mathematical process, not by a fundamentally random physical process such as radioactive decay or Johnson noise. RngPack contains
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 Robert Abbott's Mazes  Robert Abbott
Two very difficult puzzles programmed by Oriel Maxime and based on mazes in Abbott's books: the Sliding Door Maze, and Theseus and the Minotaur. Also a collection of reviews of the books SuperMazes and Mad Mazes, with more puzzles (but nothing interactive),
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 Robert's Online Applications  Robert Lum
Java applets to assist with financial investments: commissions pricer, derivatives pricer, loan pricer, option pricer, option strategy visualizer, portfolio pricer, quote sheet, stock volatility charts, and tax pricer (1999, 1998, 1997, 1996 or 1995).
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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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 Rolf's Calculator  Rolf Howarth
A fully featured JavaScript scientific calculator that includes trig functions and logarithms, factorials, 12 levels of parentheses, logs to base 2, bitwise logical operators, hex, octal, binary and ascii display.
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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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 RomanNumerals.org  John Barth
Lessons, worksheets, online games, and quizzes for practicing Roman numeral counting and arithmetic.
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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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 Room 108 Math  John Rickey
Online math practice for young children: addition, subtraction, multiplication, division; solving combinations of coins; putting numbers in order; counting to 1000, and more.
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 Rossman/Chance Applet Collection  Franciso Garcia, Carlos Lima, and Beth Chance
Applets for simulating confidence intervals for population parameter, tintervals for different population shapes, behavior of regression line, histogram bin width, sampling Reeses Pieces, sampling 2002 U.S. Senators, sampling pennies, sampling words
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 ROSSMANCHANCE.COM  Allan J. Rossman & Beth L. Chance
Workshops and presentations, publications, and current projects by the authors of the Workshop Mathematics Project textbooks. See tables of contents, instructor guides, sample syllabi and exams, and answers to activities from books in the Workshop Statistics
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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 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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 Rouse Ball's Fallacy  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
A famous fallacy by Rouse Ball now implemented in Java. A proof that an obtuse angle is right. How can that be?
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 RU4Math
Games and events for elementaryaged students from Pulaski and Montgomery counties, and Radford City schools, who participated in the RU4Math Fest of March 22, 2003, held at Radford University. Shockwave games about logic and simple equations, currency
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 Rubik's Cube Information  Michael Reid
All about Rubik's Cube  even a mailing list. Site contents include: the Nederlandse Kubus Club; Rubik's cube pages on the Web; Cube books; Sources of cubelike puzzles; the author's notes, including an optimal cube solver; other Cube solutions on the
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 Rubik's Cube Java Applet  Michael Schubart
To twist the cube, press the mouse button over a cubelet face that belongs to the slice you want to move. Keeping the button pressed, drag the mouse in the desired direction; then release the button. Moving the whole cube is done in the same way  just
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 S3Triplett als 3DWelt und als Animation  Stefan Scheller
Ein S3Triplett (drei orthogonale Projektionen) wartet mit überraschenden Effekten auf. Besonders interessant wird das Triplett, wenn es als VRMLAnimation betrachtet wird (VRMLPlug In vorausgesetzt). A GIFanimation shows a S3triplet. When watched
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 Salinon: From Archimedes' Book of Lemmas  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
A description of Archimedes' application of propositions from the second book of Euclid's Elements to mathematical proofs. An interactive Java exploration is provided.
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 Saltire Software
Mathematical technology for industry and education. Saltire Software's core technologies are constraintbased interactive geometry systems, symbolic algebra, and optimization, with products for mechanical engineering, mathematics education and layout
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 SAM Learning  SAM Learning Ltd.
U.K. exam revision (review) for A Levels (age 1618), GCSEs (age 1416) and SATs (KS3, age 1114; KS2, age 711; KS1, age 57). Draganddrop exercises and online tests of math knowledge.
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 SAMMO  Sinclair, Nathalie; Murphy, Pat; et al.
Tools for exploring, creating, and doing mathematics. Sinclair's Java applets let middle school students explore appealing mathematical situations not normally included in school curricula while using fractions, ratios, decimal numbers, and other concepts
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 Sangaku: Reflections on the Phenomenon  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
A collection of sangaku problems with Java simulations and complete solutions, preceded by an introductory article that promotes an unorthodox view point on the wonderful phenomenon of Temple Geometry.
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 SAT Free Math Practice  Roland Mfondoum
Download free SAT prep math worksheets, take autoscoring quizzes online, and watch videos on algebra and functions, factorization, polynomial expression expansion, linear equations and inequalities, quadratic equation solving, numbers and operations,
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 SAT Math Pro  Colleen King
Interactive video lessons, timed quizzes, and other instruction for SAT math preparation, categorized into assess, practice, and strategies.
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 SAT Prep Plan  Wendlink
Free SAT study content including streaming video, a custom study plan creator, and many practice problems.
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 SAT Test Prep  Ivy West
An online interactive SAT course, with animation, sound, live tutor help, and learning games.
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