Opie Sheet (formerly Sheet/Qt) is a spreadsheet software with many features such as doing mathematical and statistical calculations, sorting, formatting cells, etc. It is GPLed, so you can distribute it freely. Furthermore, it is developed for Qtopia Worldwide Developer Contest and has been a Beta Winner in the contest
NumberX is a mathematical puzzle game that will challenge your mental math abilities!
You are given four random numbers, between 1 and 9, and you must put them all together using the basic arithmetic operators in such a way as to arrive at a given target random number.
Every puzzle has a solution