 Ken's Puzzle of the Week  Ken Duisenberg
A weekly puzzle for advanced high school or college level, with a math, geometry, or game focus. The problems are easy to understand but tricky to solve. An archive of previous problems and solutions is included, together with a list of other puzzle sites
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 Key Curriculum Press
Publisher of innovative texts and software applications for teaching mathematics including the Geometer's Sketchpad (dynamic geometry), Fathom (dynamic statistics), TinkerPlots (dynamic data exploration and analysis), Michael Serra's textbook Discovering
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 KeyedIn Magazine  nelsonthornes.com
Weekly puzzles, quizzes, features of great mathematicians, fun with numbers, and strategy games. An Internet quest and "the serious stuff" offer selfscoring problems. Teacher resources provide links and ideas for each chapter of the Nelson Thornes Key
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 Kids Activities  Barak Bezalel
Freely downloadable illustrated PDF worksheets.
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 Kidsmath  About.com
A guided portal to the world of kids' internet math sites. Includes links to math sites categorized by level and topic; math newsletters (which typically highlight a group of sites on one topic, with associated articles); discussion forums; monthly problems
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 KidsNumbers  The KidsKnowIt Network
KidsNumbers' most popular singleplayer games count down against a clock: Add It Up, Lake Mathatobie (addition), Turkey Terminator (fractions), Number Drop (basic operations set to a Tetrislike challenge), St. Pat's Math Adventure (basic operations).
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 Kid's Page Archive: Free Printable Math Worksheets  Tracey Smith
Free printable math worksheets for prek through 5th graders.
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 The Kid's Pages  Rob Rogoski and Bill Pierson
Online "worksheets," each with 30 randomly generated problems in addition, subtraction, multiplication, or division. After submitting answers, get back a page of results that diplays your name, individual answers checked right or wrong, overall percentage
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 KinderIQ  Wade Luders
KinderIQ provides learning activities with immediate audio and visual feedback to help children master the earlychildhood skills needed in kindergarten. The company also provides freely downloadable PDFs of worksheets, activities, and learning games:
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 The Klein Project
Revisiting the intent of Felix Klein's Elementary Mathematics from an Advanced Standpoint on the centenary of its publication, this IMU/ICMIcommissioned project aims to produce a book for upper secondary teachers that communicates the breadth and vitality
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 KöMaL  Mathematical and Physical Journal for Secondary Schools  Hungarian Ministry of Education
A journal that first appeared on January 1, 1894. The best solutions with the names of the 1418yearold authors are printed. KöMaL regularly reports on national and international competitions, prints articles on interesting results in mathematics and
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 Knight Coverings for Large Chessboards  Frank Rubin
Knight coverings for square chessboards up to 26x26, and proofs of optimality for boards up to 10x10. The problem of how to cover a chessboard with the smallest number of knights has fascinated mathematicians and chess players for years. The problem is
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 The komplex plane  Travis Kowalski
Kowalski's problems, animations, tutorials, and other "mathlets" focus on calculus. See also the jokes collected by this professor at South Dakota's School of Mines, and his blog of math musings that wonder at the mathematics in everything from quilts
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 KrazyDad.com  Jim Bumgardner
Printable puzzles, mazes, games, and more from a selfdescribed "senior nerd" at Disney Interactive Labs: kakuro (aka cross sums, numeric crossword puzzles), krypto kakuro (a combination of kakuro and cryptograms), slitherlink, bridges (aka Hashiwokakero),
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 KRN Software
Free online games for Javaenabled browsers. Java Edutainment games require matching shapes and colors in Space Cargo and Cargo Bay, simple addition in Numeric Defenders, and odd and even number identification in Even Steven, Jr.
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 "Kryptos"  Central Intelligence Agency (CIA)
This page showcases the history and mystery of "Kryptos," a sculpture at the CIA by artist James Sanborn. See the Flash video introduction, and learn more about the sculpture, the code, and the artist. Textonly version available.
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 Kungfu Math  Kungfu Interactive Pte Ltd
This online Singapore Math portal offers worksheets, quizzes, games, and more, from data analysis, geometry, measurement, mental sums, and whole numbers to algebra, distancespeedtime, fractions, heuristics questions, percentages, and ratios.
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 Kung Fu Science  Institute of Physics
Watch martial artist Chris Crudelli demonstrate to physicist Michelle Cain how she can break a wooden plank with one strike of her bare hand. Before actually attempting the feat herself, Cain applies Newton's laws and the conservation of energy to calculate
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 kwizNET Learning System  kwizNET Learning
Automatically generated quizzes and worksheets, based on widely recognized curricula. Includes progress indicators and award certificates to keep students motivated.
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 La Biblio
Una biblioteca de textos electrónicos. Los índices adjuntos permiten navegar por una gran diversidad de temas, todos ellos relacionados con el mundo de las Matemáticas a un nivel de bachillerato o superior. De una
recopilación
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 Laboratorio Virtual de Triángulos con Cabri  Ricardo Barroso Campos
In Spanish: triangle problems proposed, and solutions via Cabri are requested.
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 Labyrinth  Peter Kishalov
An online puzzle: choose the correct door to advance through the labyrinth, based on logic puzzles similar to those published by Raymond Smullyan in his book The Lady or the Tiger?.
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 The Ladies' Diary  Ivars Peterson (MathLand)
The Ladies' Diary: or, Woman's Almanack was published annually, starting in 1704. Printed in London, it featured the usual stuff of almanacs: calendar material, phases of the moon, sunrise and sunset times, important dates (eclipses, holidays, school
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 The Language of Mathematics  Warren Esty; Montana State University
A book and corecourse at Montana State University. Site provides a description of the philosophy behind the book, the methods used in the book and course, research results from studies of both, and information on ordering the book. Also a bio of the
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 Lateral Puzzles  Paul Sloane
Pose or solve lateral thinking puzzles, also known as situation puzzles, which depict a counterintuitive scenario to be explained by asking yesno questions or by proposing explanations. Read questionandanswer conversations of current and solved puzzles;
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 The Latin School of Chicago Middle School Problem of the Week  Tom Canright
Math and logic puzzles  many original, some reproduced from sources such as NCTM journals  with solutions presented in accompanying videos.
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 LearnBop  LearnBop INC.
Oneonone online tutoring for students; infographic progress reports for their teachers and parents. See, in particular, LearnBop's autoscoring playlists of algebra and other math problems, which offer "ask for help" buttons and stepbystep guidance.
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 LearnChem.net  boeschcomputing.com.au
Organic and physical chemistry AP topics, tutorials, tests and quizzes, practice problems, and tools.
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 Learn.co.uk  Guardian Education Interactive Ltd.
Interactive resources for learners to support Great Britian's national curriculum. Selfguided lessons, with glossaries and selfassessments, for key stage 2, key stage 3, or key stage 4 cover numbers; shape, space, and measurement; handling data; algebra,
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 Learning Games and Activities for K12  Creative Teaching Associates
Over 200 nonelectronic learning games and activities for ages 4 through adult. Math products include flash cards, activity cards, board games, math chips, cards, books, cassettes for basic math facts drill, and many more. Products are also listed by
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 Learning Jolt  Robert Croisant
"Quick and repeatable" mathematics problems for students, who gain points at specific milestones which they may then use to choose their own rewards in the Learning Jolt store. With statistical reports and other tools for parents and teachers to track
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 LEARNINGlover  AfterMath
Resources to understand "the interactions between mathematics, computer science and probability." JavaScript flash cards and implementations  each with autoscoring, randomlygenerated problems, some with pseudocode  include the a priori algorithm,
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 Learning to Learn: Problem Solving  Greg Gay, Learning Disabilities Resource Community (LDRC), University of Toronto
Find out about your learning style by solving challenging arithmetic, logic, and mathematical story problems. Puzzles include analogy exercises which reveal our abilities to infer, map meaning, classify, and alter knowledge in the face of novel learning;
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 Learn Math Fast  J.K. Mergens
Sample or purchase the five volumes that explain how a homeschooling parent taught her son. The LearnMathFastBooks.com site also offers free worksheets, lessons, homeschooling articles, and other resources.
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 LearnZillion
A free learning platform that combines screencast video lessons, lesson commentaries, assessments, and progress reporting. Explore lessons by Common Core State Standard (CCSS) in math.
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 Lectures on Probability, Statistics and Econometrics  Marco Taboga
Lectures and exercises on probability theory, statistics, and econometrics. The section entitled "mathematical tools" provides overviews and examples of combinatorics (permutations, dispositions, combinations), sequences, limit of a sequence, the RiemannStieltjes
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 Lehigh University High School Math Contest  Lehigh University, Bethlehem PA
An annual contest for high school students. Results of the 19th annual contest in 1999 are on the Web, and a postscript file of the test is available. A summary of top finishers in all contests since 1981 is also provided.
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 Le Kangourou des Mathémathiques
Ce jeu de mathématiques, créé en 1991 sur le modèle du concours national australien, comporte 24 questions à choix multiple de difficulté croissante, proposées le même jour dans tous les établissements
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 Lemonade Stand  Jason C. Mayans
A Web version of the computer game Lemonade Stand: you have to decide how many cups of lemonade to make based on the weather forecast. You also have the option to advertise and attract more customers. You receive a daily report with financial information
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 Le site des maths à petites doses  SaintMartin Arnaud
Supplementary information and explanations of various mathematical topics, often illustrated with figures and JavaScript, as well as some sample problems and multiplechoice quizzes. In French.
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 Les Mathématiques  Gilles G. Jobin, Projet Diderot
Web resources, activities, lessons and tutorials for secondarylevel mathematics. Illustrated geometry theorems, with extensive use of the software package the Geometer's Sketchpad. Puzzles and games; algebra problems and adult education. Activités:
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 Les quatres opérations sur les nombres entiers  Gilles G. Jobin, Projet Diderot
An interactive course, with extensive use of the Geometer's Sketchpad. Sommaire: Introduction générale; Conseils techniques; Une définition des nombres entiers; L'addition; La soustraction; La multiplication; La division; La priorité
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 Lesson Planet: Math  Cathy Neushul; Education Planet
Lesson Planet is a search engine for teachers that provides teacherreviewed online resources including more than 26,000 math lesson plans, 10,000 worksheets, and 200 sites. Try the site free for ten days, or sign up for a site license as an individual
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 Lesson Study Communities Project in Secondary Mathematics  Education Development Center, Inc.
Information and materials from lesson plan study undertaken at Wareham High School (Massachusetts). Teachers studied and reflected on the teaching of algebra and geometry with McDougal Littell, Key Curriculum, and other content and software developers.
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 Let's Count!  Cynthia Lanius
Colorful, busy (sometimes too busy for adults, but children are drawn to them) activities for learning to count. The activities can be done either on computers with Internet access (optimally), or they can be printed out and used as a paper and pencil
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 Let's Do Math!  Cynthia Lanius
Maria and Cassie love doing math. The first problem they solve together is counting all the squares on a checkerboard  not just the individual squares, but all the differentsized squares that could be counted. Other Do Math problems include probability
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 Let's Graph!  Cynthia Lanius
Canga Rue Middle School conducted a survey of all its students to determine some of their interests. A graph illustrates the results of one of the questions. From the information provided, answer the following questions:  How many students are at Canga
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 The Let's Make a Deal Applet  West, Street; Dept. of Statistics, Univ. of South Carolina
As a motivating example behind the discussion of probability, this applet allows students to investigate the Let's Make a Deal Paradox (also known as the Monty Hall Problem, or The Three Doors). This paradox is related to a popular television show in
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 Let's Play Math!  Denise Gaskins
"As a homeschool mom who loves math, I want to help other homeschoolers see the variety and richness of the subject.... I hope this blog will be a place where we can play around with ideas about learning, teaching, and understanding math. (For me, it
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 A Level Mathematics Resource Site  Frederick Koh
Solved problem sets, summary handouts, and examination advice for A level Math students from a tutor with twelve years of teaching experience.
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