Well, Firefox doesn't seem to know what to do with a BIN file called 'play' when I hit the 'Go' button. I don't know why, but you might want to look into that. That could be a sizable slice of the market to simply ignore.
I was surprised that I actually got into the game a bit. The problems are challenging enough to make it a real race with the timer. I didn't quite expect it to be as interesting as it turned out.
This might work well as one of those IQ quiz/survey things that seem to crop up a lot in banner ads. You could push it with a slogan along the lines of "How fast is your math?" although you might want to get a bit more creative. Checking just now, I see the domain fastmath.com is already taken. In fact, it looks like there are already some games out there along similar lines. Don't expect to find a lot of low hanging fruit.
That said, I think you might still find some opportunity. I would probably look at hooking the game into Facebook to get it in front of more people, and promotion deals for self-help books targeting math skills.
You'll probably need to liven up the design, though, and you absolutely MUST make it work with Firefox, without telling or expecting the user to do or install anything. I don't know if it's a problem for anyone else, but I JUST freshly installed FF on my Windows laptop, just in case the problem was Linux, and it failed the same way there. Google Chrome handles it on Windows (as I assume does IE), and Konqueror on Linux even knows what to do with it. What Firefox is missing, I don't know, but I suspect that slice of the market is a little bit big to just ignore. You would probably do well to look into it.
Good luck!
UPDATE: Had another look with Windows Firefox, and it's identifying the file as MIME type "application/octet-stream", which is probably what my Linux version considers a BIN file. I'm also noticing that sometimes the browser does seem to dectect the file/MIME type and run the file correctly on both Linux and Windows. Less often than not, though.
At a guess, you're going to need either to set the Content-TYpe (text/html?) explicitly, or give the file an extension. Otherwise, Firefox is unlikely to handle it consistently, let alone correctly, and that's liable to KILL your chances of monetizing anything.
Again, good luck...