Same here brah. I use finger tricks for much of my quick on-the-spot arithmetic. When I was young(14-24) I could do it in my head, as the years went on I started to rely on some rote memorization and the aforementioned finger shortcuts. These days (in my 50's) I unabashedly use the shortcuts and don't care what wtf anyone thinks...of course the gray in my beard stops most people from razz'in me.