out of curiosity, was this only something while trying to "do it in your head" or also when doing it long form on paper. which is a question I was asked a lot, but I hated. Even when doing long form on paper, there's still numbers floating in my head.

It took until I started receiving partial credit for showing work before I'd stop doing the entire thing in my head. Bad math teachers thought I was cheating while the good teachers saw me working it out but convinced me partial credit was a good thing.