We’re using a fantastic math curriculum called Math Mammoth for Levi. The vast majority of math concepts are self-taught with Math Mammoth, which makes it very easy for us to use. Even with Levi’s dyslexia and processing disorder, he is able to follow the simple text instructions with pictures for each lesson, and he can complete much of it without even asking me for help. I can’t say enough good things about Math Mammoth! I’ll have a review of the curriculum for you soon, but for today, I’d like to talk about one concept that Levi had a little more trouble with – borrowing or regrouping in 3-digit subtraction.
He can usually manage two-digit subtraction with borrowing or regrouping, but tends to get confused when three digits are involved. The way it was explained on the three-digit regrouping and borrowing Math Mammoth lesson was a little confusing to him. Frankly, I wasn’t sure if I could adequately explain it based on the MM instructions, either. The point, of course, is to know how to do the equation, not to do it in a specific way, so I went in search of other ways to explain the concept.
Here are a couple of videos that show various ways to handle three-digit subtraction. The first is from Khan Academy. I like how the numbers in the ones, tens, and hundreds columns are shown in different colors so that it’s more obvious where you’re borrowing from – the visual help is important for kids like Levi who struggle to focus on the information they need.
I found the second video on WatchKnowLearn.org, which is an amazing site with videos on almost any educational topic. I liked “Subtracting – Working With 3-Digit Numbers,” but there’s also a good one about subtracting with 1- to 4-digit numbers and another about using addition to check your work. Levi likes to watch videos, so we watched several until his attention started to wane.
On Pinterest, I found loads of suggestions for teaching regrouping with 3 digits. We have some Cuisenaire rods and some sets of Legos that we reserve just for math manipulatives, so we tried making a page with three columns and using the rods or Legos to represent tens and ones. That method was similar to the picture instructions on his Math Mammoth lesson.
Lately I’ve tried to add memory aids around our workspace, to help ideas stick in his mind and to help him refocus when he gets confused. There are lots of versions of this mini-poster around the web, but none of them were quite what I wanted. The best one specifically said it was for 2-digit subtraction, though, and concrete thinkers (like my Levi) might then struggle to get past that 2 sitting there when they’re working on a 3-digit problem. Fixate much? Yes, we do! That may be hard to understand if your child doesn’t think that way, but trust me – it’s a thing. Hand some kids a poster that says it’s for a specific thing and they will not be able to translate that skill to a similar task. Hence, my newly created poster.
If you’d like to use this fun, colorful regrouping reminder in your homeschool, I’m offering it to you free. You can print it on a regular 8.5×11 paper, or if you want to get a little crazy, it would work on larger paper, too. Click for the PDF – Subtraction Borrowing Reminder Poster.
I can see that a lot of you are finding this post through search, and I’m really excited that you’re here. If the poster or video suggestions were helpful to you, please leave a comment and let me know, or consider sharing the post on your social accounts. I’d love to hear from you!