Good point. I keyed into the method ("For example, start with 432. Split into 43 and 2. Subtract 4 from...") more so than the theory of the original article. It

Good point. I keyed into the method ("For example, start with 432. Split into 43 and 2. Subtract 4 from...") more so than the theory of the original article. It reminded me of these wacky (ingenious?) shortcuts for doing basic math that I recall reading about. Sorry no reference on those. As far as I remember, they involved some form of shifting numbers around, transposing digits, drawing grids, etc. These were before calculators (er, phones) were in every pocket. I think calculators were just starting to show up on snazzy watches at the time I was learning these math shortcuts.