 Sliders  Cut the Knot!, Alexander Bogomolny, with Don Greenwell
A variation of the Fifteen puzzle invented by Sam Loyd in the early 1870's: puzzles on graphs, including a proof independent of Wilson's theorem that all Lucky 7 permutations are possible; and variations of Sliders, a Fifteenlike puzzle that can be played
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 Sloan Digital Sky Survey
The astronomical surveys of the Sloan Digital Sky Survey (SDSS) have "obtained deep, multicolor images covering more than a quarter of the sky and created 3dimensional maps containing more than 930,000 galaxies and more than 120,000 quasars." SDSS's
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 Slocum Puzzles  Jerry Slocum
Puzzle collector and author's site. Features puzzle descriptions, shop, descriptions of books written by Slocum and collaborators, and a history of Slocum's famous Puzzle Parties.
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 Smartkiddies Mathematics  Andy Hobeika
Free interactive lessons, number challenge exercises, worksheets  and visual reporting for instant feedback. To begin, select a year (one through seven, corresponding to Australia's curriculum), then a module, ranging from whole number to position &
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 Smartkiddies Mathematics  Smartkiddies Mathematics
Video lessons, interactive activities, maths games, number challenge drills, worksheets, assessments. Developed by experienced Australian teachersall content is based on the Australian curriculum. Free to all schools and teachers during school hours;
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 Só Matemática  Só Matemática
Material para ensino fundamental, médio e superior, além de provas online, biografias de matemáticos, trabalhos de alunos, um acervo de softwares matemáticos, artigos, jogos, curiosidades, histórias, fóruns de
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 Snap Math  John and Eva McKendrick; Teilhard
A version of the children's game, but to win the cards, you have to do the math. Click on the pack at the left to start; when your card matches the computer's card, you are set a series of math problems. If you answer correctly, you win the cards.
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 snark (Spanish Math Puzzles)  Universidad de Buenos Aires, Math Forum
Contributions are only in Spanish. Una lista de correo electrónico dedicada a la matemática recreativa, los problemas de lógica recreativa, juegos de tablero y problemas sobre ellos, rompecabezas geométricos (poliominós,
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 The Snowflake Curve, Perimeter and Area  Don Cohen (The Mathman)
Young children start with an equilateral triangle, then go 1/3 of the way along each side, then add a smaller equilateral triangle, protruding out from every side to get the next figure. A sample problem with answers from Chapter 4 of Don Cohen's worksheet
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 Soap Films and Grid Walks  Ivars Peterson (MathLand)
A simple, physical demonstration of a mathematical truth can produce a lasting impression  one that inspires new questions and speculations. For Christopher C. Chang, a student at Henry M. Gunn Senior High School in Palo Alto, Calif., and one of 40 finalists
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 SoftSchools.com  Mani Gudavalli
Free math worksheets and interactive online games for practicing times tables, adding, subtracting, telling time, and more. Organized into prek, kindergarten, grades 12, grades 34, grade 5, measurement, and fun games.
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 Software  Bill White
These Flash apps provide online practice deriving some unknown property of a figure given its other measures. Find the area of a trapezoid given its two base lengths and height; find one of its bases given its area and height; find its height given its
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 Solutions to Heinemann AS/A Level text books  George Ierotheou
To provide ample examples of how to apply the key methods and techniques used at AS/A level.
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 Solve for n  NASA Lewis Learning Technologies Project
Solve for n: 3/n = 7/12. A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Solve for y  NASA Lewis Learning Technologies Project
Solve the following for y: 12y  16 = 20y. A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 SolveMe Mobiles  Education Development Center, Inc. (EDC)
Colorful interactive hanging sculpture puzzles that challenge prealgebra and algebra students to balance equations by solving for unknown values. Freely solve over a hundred prehung mobiles or build your own and then contribute them to the SolveMe community.
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 Solve My Maths  Ed Southall
Blog of "puzzling questions that purposefully minimalise the amount of information explicitly given," written by the author of Yes, but Why? Teaching for Understanding in Mathematics. Posts by the University of Huddersfield maths education specialist's
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 Solve My Math  Solvemymath
Online math integrals calculator, derivative calculator, function grapher, math formulas and facts, math quizzes and puzzles.
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 Solve This!  ThinkQuest 2003
Information about eight famous mathematicians, with interactive quizzes, static problems and games.
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 Solving Equations  Don Cohen (The Mathman)
Make equations or open sentences true by guessing. Equations with X's on both sides; quadratic equations (11 ways to solve a quadratic equation); using balance pictures to solve equations. Sample problems with some answers from Chapter 8 of Don Cohen's
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 Solving Inequalities with One Operation  Internet Academy (IA)
Stepbystep instructions for learning how to solve and graph inequalities, with problems and solutions.
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 Solving Math Word Problems  Hal Schneider
A selfhelp tutor for grades 612, remedial math (all levels); and adults. Chapter titles: Elementary Math Rules; Working with "ONE"; Working with Fractions; The ' Word/Fraction' Technique; Elementary Algebra, Factoring & Ratios; Common Forms of Equations;
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 Solving On Line problems of Inventory Control  G.B. Rubalsky
Online solver for special optimization problems, plus samples of problems, solution methods, algorithms and programs, which might be of interest to those involved in operations research, numeric optimization and stochastic processes.
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 Solving Quadratic Equations  Prakash Sukhu
Introduces the general form of the quadratic equation, and shows how to solve the quadratic equation step by step. Includes methods of factorisation and completing the square, questions to test your knowledge, and an online equation solver with which
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 Solving the Rubik's Cube  Matthew Monroe
Instructions, popularized by Minh Thai, the National Champion cube solver, for solving a 3x3x3 Rubik's Cube. Also, instructions for how to solve a cube when it has oriented pictures on each face. Directions for solving a 2x2x2 Rubik's mini cube, the professor
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 Solving Word Problems: Applications of Exponential and Logarithmic Functions (S.O.S. Mathematics)  Dept. of Mathematical Sciences, Univ. of Texas at El Paso
To solve an exponential or logarithmic word problem, convert the narrative to
an equation and solve the equation. Includes discussions of problems dealing with interest rates, mortgages, population, radioactive decay, and earthquakes.
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 The Soma Cube Puzzle  Modvix
Purchase the Soma Cube. Piet Hein, a Danish poet and inventor, visualized the set of all irregular shapes formed by no more than 4 cubes, each of the same size, and realized that the seven simplest irregular combinations of cubes can form a larger Soma
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 Some Problems in Matroid Theory  Thomas Zaslavsky
Sources of problems compiled by Zaslavsky, and problems he's found interesting: Bonin's Projective Bound; Maximum rFlat; Covering And Packing by Flats. For general sources of information on matroid theory, see Matroid Miscellany.
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 Some Problems & Puzzles  Nancy Casey
Problems inspired by math books (Instant insanity; Penrose rhombs) and friends Larry Copes and Mike Fellows (BikePed, Idaho  also known as Muddy City).
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 Some (Unsolved) Mathematical Problems  Jörg Winkelmann
A collection of some analysis questions the author encountered in the context of his own research.
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 Some Variations on the Theme of Polyominos  Recmath
Patterns that illustrate how the squares of polyominos are connected to each other. Examples of polyominos with a grid superimposed to illustrate the individual squares; with a line that joins the midpoint of two adjacent square if the squares are connected.
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 Sources in the history of algebra: arithmetical and recreational problems  Albrecht Heeffer
A comprehensive database of arithmetical and algebraical problems from sources before the 18th century, for research and educational use.
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 The Southwest Center for Arithmetic Geometry  Romyar Sharifi, Principal Investigator
In this intensive fivedaylong school, advanced graduate students work closely with senior faculty and postdoctoral fellows — not as individual researchers presenting their work in relative isolation, but in highly participatory, extended courses
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 Space Educators' Handbook  Jerry Woodfill, NASA Johnson Space Center
For Mac or PC: programs that include more than 2000 files interactively linked for ease of learning about NASA, space science, space history, and space technology. Many well designed and extensively educational files are available from this Web site,
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 Space Math  Dr. Sten Odenwald
NASA offers realworld problems about astronomy and space science, for students in grades 68 and 912. The problems are in PDF format, and searchable. They are often based on press releases and cover topics from black holes to space weather and the search
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 Spinning to a Rolling Stop  Ivars Peterson (MathTrek)
The underlying mathematics of spinning disks. Spin a coin on a tabletop. As it loses energy and tips toward the surface, the coin begins to roll on its rim, wobbling faster and faster. Toward the end, the coin generates a characteristic rattling sound
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 Spirals of Primes  Bryan Clair, University of Chicago
This page will generate a spiral of numbers, with the primes marked as stars, and the composites as dots. The center of the spiral is marked with an 'X'. Specify the number at the center of the spiral below, and the width (and therefore also the height)
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 Spreading Memes  Cut the Knot!, Alexander Bogomolny
First of a series of interactive columns for MAA Online that use Java applets to simulate a puzzle or mathematical problem, one not stated directly since the applets are intended to be such that the right answer to an as yet unstated problem should be
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 Spreadsheet Math  Sustainablearning, Inc.
Spreadsheets as laboratories where students can "become a scientist who poses a question, builds a model, collects data, and asks 'What if ...?'" Freely downloadable Excel files that emphasize student choice, challenge, and creativity range from place
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 Statbag  Worth Swearingen
A blog repository for statistics educators: "... each teacher should have a bag of tricks. Teachers spend years developing their own favorites. While acknowledging that experience is the best teacher, one purpose of this site is to help teachers develop
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 Statistical Rules of Thumb  Gerald van Belle
This companion website to Statistical Rules of Thumb, published by John Wiley & Sons, Inc., offers free PDFs of chapter two ("Sample Size") and more than a dozen "monthly rules of thumb," such as "Use Text for a Few Numbers, Tables for Many Numbers,
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 STATISTICS.COM
A source for information about statistics software (major packages like SAS, SPSS and SPLUS, shareware, and smaller packages), as well as about statistics analysis, data analysis, and short courses in statistics  messy data, design and analysis of experiments,
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 Statistics, Measurement Uncertainty, and the Number of Galaxies in the Universe Lab  Dennis Zaritsky; Univ. of California at Santa Cruz
From a course in observational astronomy, a lab for exploring some basic issues regarding statistics in astronomy and measurement uncertainties, and finally
produceing an estimate of the number of galaxies in the Universe (with its associated uncertainty).
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 StatsLife  Royal Statistical Society
A professional body for all statisticians and data analysts that, since its foundation in 1834, promoting the importance of statistics and data. Publishers of Significance magazine, StatsLife freely offers resources for teachers, a glossary, and much
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 StatsMonkey  Jason Molesky
Notes and resources to assist Advanced Placement Statistics teachers and students. "TPS Resources" include packets, handouts, worksheets, activities, vocabulary crossword puzzles, and Jeopardy! PowerPoint Reviews to accompany The Practice of Statistics,
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 Stat Trek
Free, online tutorial covers basic statistics, probability, distributions, sampling, estimation, and hypothesis testing. Includes online calculators, sample problems with solutions, and glossary of statistical terms.
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 Stayorswitch.com  Jeremy Jones
Game simulation and animated explanation videos of the Monty Hall problem. A blog by Jones, who teaches high school math, dates back to February, 2014, with other probability puzzles.
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 The Steiner Tree Page  Joe Ganley
The Steiner tree problem is a minimum interconnection problem. The most basic
version is in a graph: given a weighted graph in which a subset of vertices are identified as terminals, find a minimumweight connected subgraph that includes all the terminals.
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 Stella's Stunners  Rudd Crawford
More than 600 nonroutine mathematics problems named in honor of the Dutch baroness Ecaterina Elizabeth van Heemsvloet tot Schattenberg. Each collection in the Stella Library contains five subsets, one for each course of PreAlgebra, Algebra I, Geometry,
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 STEM Sheets
Makers of printable flash cards. Choose number ranges, and whether or not to include answers, before freely downloading PDFs of addition, subtraction, multiplication, or division problems.
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