Used this to figure out the weightings of the columns in one of our market research studies.

Quoted: solves your linear systems, including systems with parameters. This is the main site of WIMS (WWW Interactive Mutlpurpose Server): interactive exercises, online calculators and plotters, mathematical recreation and games

While on the topic of math....

Quoted: Aside from probability and discrete math, there are a few other branches of mathematics that are potentially quite useful to programmers, and they usually don't teach them in school, unless you're a math minor. This list includes:

Interesting paradox.

Quoted: How much can you expect to win, on average? With probability 1/2, you win 1 dollar; with probability 1/4 you win 2 dollars; with probability 1/8 you win 4 dollars etc. The expected value is thus [graphic omitted]. This sum diverges to infinity; "on average" you can expect to win an infinite amount of money when playing this game.

Quoted: Assuming that birthdays are evenly distributed throughout the year, if you're sitting in a room with forty people in it, what are the chances that two of those people have the same birthday?

Quoted: Fibonacci numbers in mathematics, formulae, Pascal's triangle, a decimal fraction with the Fibonacci numbers. Puzzles and things to do, for schools, teachers, colleges and university level students or just for recreation!