We have to distinguish between craft and when we need a functional outcome. Personally, I'm not interested in the craft of mental math. When I'm trying to calc

We have to distinguish between craft and when we need a functional outcome. Personally, I'm not interested in the craft of mental math. When I'm trying to calculate the tip I want the answer quickly so I can move on with my life. But if you care about the craft of mental math, then by all means, go for it