The Action of Subtraction

I thought that I would have the hardest time teaching my students how to subtract with regrouping this year, but it went surprisingly well. There are a couple of little memory tricks I taught my students to help them remember when to borrow.

First, I used this flipchart when I introduced it to my students and they TOTALLY got it! (Warning: You may need to download the Promethean software to use this.)

You can also use the four B’s: Bigger Bottom, Better Borrow!

I recently saw a mnemonic for subtraction in a flow chart. With regrouping-”More on the floor, Go next door and get 10 more.” Without regrouping-”More on top, no need to stop!” I will probably make a poster with this for next year because I had fifth graders last year who would try to borrow when they didn’t need to. I think that once you teach regrouping, students think they need to do it all the time.


As a result, I began starting out each lesson by showing them a problem and asking them whether or not they needed to regroup. I think this really gets them thinking about it before they do other subtraction problems. Some kids just get lazy and don’t really stop and think about what they need to do. They just assume that since you’ve been learning regrouping, that you just regroup all the time. It’s very frustrating! You teach them a skill and they absolutely get it, but some of them can’t apply it only when it’s necessary.

Here are a couple of songs --

To the tune of "If You're Happy and You Know It"

If it's smaller on the top,
Take a ten.
If it's smaller on the top,
Take a ten,
If it's smaller on the top,
Take a ten and start again.
If it's smaller on the top,
Take a ten.

Subtraction Song powerpoint by yours truly. You'll have to excuse my singing voice. =)

I love rhymes and songs and I wish I had them for everything, but I’m just not that creative. If you know of any other subtraction memory tricks, please share!