content: Whether we like it or not, there is also the issue of practicality in light of the fact of technology today. Just on principle alone, it is worthwhile to teach kids how to multiply 4 digit numbers by other 4 digit numbers in the old way. Sure, I get that. But at the same time, how much we stress it is another question. In a world where calculations of this sort are so easily computed by calculator, how realistic is it that we lose the availability of technology to do it? Yes, if the world falls apart we will need the ability to perform calculations, but at the same time, things like percentage math and proportions are going to always be a lot more practically important than multiplying 4 digit strings, and that sort of puts an upper "practical limit" on how long the strings to be multiplied are really going to be. There aren't many real-world examples where people are multiplying 4 digit strings by other 4 digit strings. It is much more applicable, in the base 10 system anyway, to be demonstrating multiplication by numbers less than or equal to 100, along with the properties of decimals. Also kind of important here. The guy in the video is just doing the calculation. He isn't teaching it. It would have been more telling for him to show himself simulating teaching his method to a class of young people. Believe me, that isn't me defending the common core standards. They are insane. If I were the teacher, I'd be showing the written method we all learned, while also showing the "mental" process. Both are useful to know. She is essentially already teaching a convoluted version of the "mental" method.