Thursday, April 9, 2015
Troubles with Regrouping (Carrying in Addition)
Sometimes math can seem like a foreign language, to students and even some teachers. I have always loved math, and thought about things mathematically, but after becoming a teacher and a mom, you can see first hand, that not all brains think alike. And not all methods will work for everyone.
Here is an example from a typical day working with a student (sometimes even my older students make this error.)
Now, you might argue that the person could have just used a calculator, but that isn't the point here. It is good to be able to do some calculations quickly in your mind. And it is good to have number sense about how things work. We can get into why I think these things are important in another post, because instead, I would like to show you another way of thinking through this problem that might just help.
When I was in school, I was taught to "carry". These days I think they are calling it "regrouping" because you are taking a group of ones and writing as a ten. You might remember writing a little one on top of the 6 because 7 + 8 = 15 and we have 1 ten and 5 ones. This method is great and works for many people. And I am not saying you should stop using it. I still do.
What I am saying is that this method doesn't click for all minds. If you have a child or student struggling, it may help to work it out all underneath the line. So when you add 7 + 8 and get 15, you actually write 15. And then when you add the 6 and 4 you think of them as 6 tens and 4 tens or 60 and 40 to make 100. Finally, you would add these together to get 115.
This builds on the knowledge and understanding of place value. We want students to see what each digit stands for in the problem and make sense of the answer.
If you have a little one having some trouble adding two or three digit numbers, you might just want to give this technique a try. Let me know if it helps.