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Numerous puzzles, links, puzzle solver, and a generator.

Polymorf - Symmetry of Polyhedra (Popularity: )

A demonstration of the symmetry and transformational properties of the Platonic and Archimedean solids.

The Contest Center (Popularity: )

Classic puzzles and riddles requiring only simple logic and elementary math.

Mixed Up Math (Popularity: )

Logic problems, where equations are mixed up. In various formats like boxes, crosses, diagonals, mazes. ...

Math Forum: Geometry Problem of the Week (Popularity: )

Past archive and solutions. Recieve help from mentor.

Math Forum: Precalculus POW (Popularity: )

Weekly math problems and solutions from Math Forum.

Logicville (Popularity: )

Educational puzzles, brain teasers, and word games such as anagrams, cryptograms, alphametics, doublets, tangrams.

Aha! Puzzles (Popularity: )

Puzzles, books, games and tests with designed by Lloyd King, author of "Test Your Creative ...

Math Forum: Algebra Problem of the Week (Popularity: )

Past archive and solutions. Recieve help from a mentor.

Purdue University Problem of the Week (Popularity: )

Weekly math challenge with past problem archives and solutions.

Brain Teasers by QBrute (Popularity: )

Original brain teasers with solutions.

The Puzzling World of Barry R. Clarke (Popularity: )

Brain teasers, articles and puzzles forum.

Storkey: Two Envelope Paradox (Popularity: )

A tough but simply defined problem which demonstrates key issues in probability.

Paul Hsieh's Puzzles (Popularity: )

Logical and mathematical brain teasers, with an indication of difficulty. Hints are provided; solutions are ...

Math Forum: Problems of the Week (Popularity: )

Projects from the Math Forum presenting weekly interactive math challenges to accumulate points for bronze, ...

15 Puzzle of Sam Lloyd (Popularity: )

Play online Sam Lloyd's "15" puzzle The funny story of this game Mathematical implications of ...

A Primer on Cryptarithmetic (Popularity: )

Instructions, examples, references and links.

John Handley High School Problem of the Week (Popularity: )

Weekly math problem with solutions and archive.

Calculus-Help Problem of the Week (Popularity: )

Calculus based problems range from easy to difficult.

IBM Research Ponder This (Popularity: )

A monthly on-line competition hosted by researchers at IBM.