The time it takes to solve a problem is a way of measuring complexity. Many problems have no discovered solution and are therefore classified as an open problem.

Interactive go problem database and community. Solve go problems through a Java applet, add new problems, search, comment, and more.

The concept of "wicked problems" was originally proposed by Horst Rittel (a pioneering theorist of design and planning, and late professor at the University of California, Berkeley ...

Challenging word problems, spanning basic math to differential equations. ... Formerly known as Shack's Math Problems By Michael Shackleford, A.S.A. Welcome to my site of math ...

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