As a 2nd grade teacher, I can’t tell you how many times I’ve had students come to me SO excited because they can do two-digit & three-digit addition (and subtraction). Almost every time they show me their impressive skills with the standard algorithm. YAY!
As most teachers do when this something like this happens, in the back of my teacher brain, I always ask myself how deeply do they understand what they’re doing? Can they demonstrate another way to solve these types of problems? What strategies are they using? Are they doing any mental math?
It’s absolutely essential that we make sure our students have a deep understanding of what they’re doing. We work on developing this deep understanding in a few different ways.
Goodbye Standard Algorithm: Hello, Base Ten Blocks
When I start teaching two-digit and three-digit addition and subtraction, I always begin by using these blocks. Some students catch on to this very quickly and others take a little bit longer. Having students model problems with base 10 blocks helps them truly see exactly what they’re doing!
Just because you eventually move on to another strategy, some of your students still need these for reinforcement. There have been so many times when a student needs help with a problem and I have to ask them to get out base ten blocks to help them.
Repeat after me: I will keep base ten blocks easily accessible all year long.
Goodbye Standard Algorithm: Hello, Decomposing Numbers
Decomposing numbers sounds more intimidating than it actually is. When I am talking to students about decomposing numbers, I also use words and phrases such as break it down and expanded form.
Not going to lie… decomposing numbers is my FAVORITE. I always feel like this is how my brain works when I’m trying to add or subtract numbers in my head. I mentally add tens in my head before adding the ones.
Number talks are a great way to get your students decomposing numbers, and they may not even necessarily realize they’re doing it! I call that a win! I love to use these number talks as mini-lessons for decomposing numbers. In these number talks, I create strands of addition problems that build in difficulty.
You can download a free copy of these addition number talk mini-lessons! In the download you’ll get my detailed overview of how and why these were created, as well as 2-digit addition number talks to try out in your classroom!
This free resource is available in both printable and digital versions. Just click the image below & leave your email!
Yes, There Are More Strategies!
Base ten blocks and decomposing numbers are just two ways I work with my students on developing a deeper understanding of addition and subtraction. We also learn how to use the hundreds chart and number lines.
Want to help your students develop more strategies for 2-3 digit addition and subtraction? I’ve got you covered in this resource!
Related post: Teaching 2-3 Digit Addition Strategies