Exactly. I think lots of people, including myself, who become proficient in arithmetic, “do it in our head” using these constructs. It’s the fastest way to do it, but not if you’re doing it on paper. They’ve got this back asswards.
“but not if you’re doing it on paper. They’ve got this back asswards.”
Exactly! I only use it for in my head math. However, this might be the way to teach kids how to do it????????? The other examples were goofy!