This is a long video but well worth your time. Pay special attention to Bill Evers who is on the Trump Education Transition Team. This is so enlightening.
To learn about how sloppy the math curriculum is that Washington DC is cramming down our throats, Evers starts explaining it at 11:06 into the video.
If you are interested in reading more about just where this Common Core nonsense started, politicians and activists who want centralized control of education, a few far left billionaires and big education companies came together and decided to cram it down your throats. The talking points from those pushing Common Core about how it started are mostly demonstrable lies exposed by a couple of hours researching the topic using any search engine.