[hf]

On Debian (and, I'm sure other distributions of GNU/Linux) the 'bsdgames' package contains a simple program called 'arithmetic' which poses similar challenges, albeit reduced to the most elementary operations: addition and substraction. Call as

    arithmetic  -o '+-x/'

in order to add multiplication and division.

I find it a handy supplement to 'gtypist' in order to train touch-typing of numbers.

On a side-note: I'm surprised at how scarce such software is - pitiful as it may be. But then, the advancement of the human intellect isn't at the forefront of our cultural conscious, is it?