This is a way of doing mental math, and remarkably similar to how I have been doing mental math for decades (I'm a 50 year old engineer), so this method is not unique to common core.
The best mental math is the old way.
For you, maybe. I can only hold so many digits in my head at once. Beyond that, I resort to tricks, like the lesson shown above. It's a valuable skill to teach, even if you don't think you have any use for it.
Knowing your addition and multiplication facts down cold, by memorizing them.
You are assuming basic addition and multiplication tables aren't also being taught, and memorization drills given. And again, only so much can be memorized. Beyond that, I rely mental math tricks.
Of course there are mental tricks to use.
However, the kids are not going to be carrying around number lines with them everywhere.
When my son was in high school a few years ago, he could mentally out math any kid in the school. While they were fussing around on their calculators, all getting different answers, he had the answer in a few seconds. They didn’t have a clue how he did it.
We homeschooled and used Saxon Math. Those public school kids were *educated* on Everyday Math, which looks like genius level compared to the examples of what I’ve seen coming from Common Core.
I’ve yet to meet a teacher who doesn’t hate it with a passion.
Here in NYS, liberal capital of the country, our Democratic very liberal assemblyman, sent out a mailing urging people to contact the state senate and urge them to delay the implementation of Common Core in NY.
It’s so bad the teacher’s unions here are opposed to it.