Can you explain this one?

Beats me. At first I thought that every number ended up a certain symbol, but that wasn't it. There must be some kind of pattern. I even tried clicking without doing the calculations, and a different pattern appeared each time.

That's what I saw too, but I still don't get it!

Ok, what happens is that every time you try again the numbers that are always going to be the answer change symbols. As soon as you reveal the answer it removes the list of symbols to make it harder to spot.

Here is one that works the same way but is a bit easier to see the gimmick.

http://www.able2know.com/waggery/mindreader.htm

Thanks Craven! None of my friends could figure that out.

A math riddle- answer is always a number out of the timetable 9 (18, 27,..) and then changing the symbols.

Nice one, it took a couple of goes, but i saw what was happening.

LOL, wasn't too impressive was it?