I use the methods in the first two examples all the time to do math in my head. So does my Shanghai born and educated ladyfriend. But the other examples are just stoopid!
7 plus 7 and they have to make it difficult to explain. It’s simple math done in your head and for young kids add them on their fingers
“I use the methods in the first two examples all the time to do math in my head.”
So do I. In fact I was teaching them to Little Flash A last night. But I don’t call them “number bondage”.
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.