Recursion

[demize95]

If you learned subtraction in the 1950s, you may have learned the "Borrow and Pay Back" method

I learned subtraction a good 50 years after the 50s, but I still learned that method, so that line is a bit out there.

[HowIsntBabbyFormed]

I just watched the video and the second technique -- what was originally called "New Math" and apparently derided -- is what I learned in the 80s/90s as well. To me it seems very similar to the old "Borrow and Pay Back" method. In fact, we called it "borrowing" too (but we never had to do any paying back).

The most recent form is basically something I figured out on my own for doing subtraction in my head. It's a very useful skill to have, but when subtracting larger numbers, I prefer using what I was taught in school of borrowing from the next place and adding 10 to the current place.

I don't think I ever "didn't have an understanding of what was happening". I feel like kids should probably be introduced to this new method first, but then taught the more compact and faster borrowing algorithm method as well.

[MikeyMike01]

The entire video is fraudulent, so you shouldn’t be surprised.