The break apart strategy helps students see how they can split numbers into tens and ones to make adding 2-digit numbers easier.
I’ve put together the resources and support below to help you teach the strategy, give students practice, and address common mistakes.
The break apart strategy can help students make sense of 2-digit addition because they can see how numbers are made up of tens and ones. A few simple teaching moves can make the strategy even more effective.
Start with numbers that don’t require regrouping.
Give students problems where the ones can be added without making a new ten. This gives them a chance to practice breaking apart numbers and adding the tens and ones separately before adding the extra step of regrouping.
Have students break apart each number first.
Before they start adding, ask students to show each number as tens and ones. This helps them focus on the value of each digit and prepares them to add the parts separately.
Ask questions that help students explain their thinking.
Instead of just asking for an answer, try questions like, “How did you break apart that number?” or “What are you adding first?” This encourages students to think about the numbers they are working with and explain how the strategy works.
Make regrouping about the math, not a rule to memorize.
When the ones add up to 10 or more, have students notice that they can make another ten. Talk about where that new ten comes from and how it changes the tens and ones they are adding. The goal is for students to understand why regrouping is needed rather than simply memorizing a step.
Connect the strategy to the written work.
Once students are comfortable breaking apart numbers, connect their thinking to the addition they write. Point out how the tens and ones they added match the parts of the numbers in the written problem. This helps students understand why the strategy works instead of simply following a procedure.
The break apart strategy can make it easier to see what students understand about place value and where they may need more support. Here are a few mistakes you may see when students use the break apart strategy to solve 2-digit addition problems.
What you might see:
A student breaks apart 34 as 3 + 4 instead of 30 + 4, or they use the digits without considering their place value.
What’s happening:
The student may recognize the digits in a 2-digit number but isn’t yet connecting each digit to its value.
What can you do?
Have the student build or draw the number using tens and ones. Ask, “How many tens are in 34?” and “How many ones?” Then have them write the number as 30 + 4 before they begin adding.
What you might see:
A student breaks apart the numbers but combines a tens value with a ones value, such as adding 30 + 4 + 5 without keeping track of which parts belong together.
What’s happening:
The student understands that the numbers can be broken apart but is still working on organizing the parts and adding them by place value.
What can you do?
Have students group the tens together and the ones together before adding. Ask, “Which parts are tens?” and “Which parts are ones?” This helps students see that they are adding like place values together.
What you might see:
A student correctly adds the tens and ones separately but doesn’t recognize what to do when the ones total 10 or more.
What’s happening:
The student may understand how to break apart the numbers but isn’t yet connecting 10 ones to 1 ten.
What can you do?
Have the student represent the ones and notice when they have enough to make another ten. Ask, “What can we do with these 10 ones?” Then connect that new ten to the tens they already have. This helps students understand that regrouping is a way to represent the same amount differently.
If you don’t want to make your own worksheets, I have a few resources that go along with this strategy.
If you’re teaching 2-digit addition and want all of the pieces ready to go, I’m putting together a 2-Digit Addition Toolkit that brings the strategies, practice, error analysis, and teacher support together in one place.
I’m still putting the finishing touches on it, but you can join the waitlist and I’ll let you know when it’s ready.
The Toolkit will include:
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Want to be the first to know when it’s ready?
