Nope, not a teacher. I don't have the patience with people to be a teacher. I'm afraid I'd throw a smart-ass student out the window. When I see some for math short cuts, I like to expand on it to see if it will work even further. When I'm alone I have time to figure out ways to make things work. I saw another one yesterday, but I have yet to find a way to expand on it. I might post it without expanding. Plus, I'm working on another percentage one so one of the numbers do not have to end with "0".