So, earlier in the week, I saw a really weird thing that I didn't quite understand, and I shared it and was ready to clutch my pearls (FINALLY!), but alas, it was not to be. Turns out that silly math problem going around the internet is a bad example, but even if it wasn't, IT'S STILL NOT HARD, and IT ACTUALLY MAKES SENSE. It's true. They even convinced me (since I taught myself to do it later in life but didn't even know it) and I LOVE me some one-carrying.
Emily Blanton of Teaching Ain't For Heroes takes us through the SUGGESTED common core practice that is the "new" way.
I'm sure you've seen it by now. There's some picture floating around Facebook about "Common Core" math with the "Old Fashion Way" and the "New Way" to do math. In case you haven't seen it, here it is:
Yes, lots of people are losing their minds over this. And you know, it might look confusing at first, but it doesn't take much to figure out that this is a way to introduce metacognition to students to help them with their mental math. You do this in your head and you don't even realize that you do it. This blog post is the best explanation I've seen of how you do it all the time. When you go to the store and buy things, you don't bust out a calculator or get a pencil and paper to do it the "Old Fashion Way" carrying your ones and such. You make the numbers easier to manage in your brain.
Who taught you to do that? Did you learn to do it on your own? I mean, maybe you did. Maybe a parent told you. I know I learned it at school. If no one ever taught you to do that and you never figured it out on your own, people doing mental math must look like freaking wizards. Which is exactly what a lot of students who into high school math without learning mental math see their math teachers.
Math isn't the only place where students need mental exercises. We do it in English and Language Arts as well. How do you make inferences? When did you learn how to make them? Someone taught you or you picked it up naturally. Some students make it to high school completely at a loss of how to make inferences without being walked through it.
Yes, there are "easier" ways to do math using pencil and paper. However, the purpose of assignments in school is not to find the right answer. The point is to teach students how to find the right answer. If the purpose was finding the right answer and nothing else, you never would have had to show your work back in algebra. But you had to show your work so your teacher could see if you made a mistake along the way so they could help you fix it. Learning mental math is the same way. And practice makes perfect, so get used to seeing it for awhile.
I'd also like to point out that the example being passed around was likely made up by someone who doesn't actually teach this method. The first thing someone teaching this would say would be to cancel the twos in the ones position.