One of the most important concepts 2nd graders will learn in math is subtraction with regrouping. Although math is not taught the same way it was when many of us were in school, that doesn’t mean it’s a bad thing! Before students dive into subtraction with regrouping strategies, they must first understand the why behind the math concept.
That’s the biggest difference in today’s math versus the math of previous generations. It’s all about problem solving and knowing the reasons behind the strategies and operations.
This gives students to power to choose the strategies that work best for their learning style. This is important because not all students learn the same way. Read on for tips on teaching 4 strategies for helping your students master subtraction with regrouping.
How to Introduce Subtraction with Regrouping
Learning the 4 subtraction with regrouping strategies will be new for many of your students. In order to introduce this concept and these strategies in a way that’s easy for students to digest, I like to use a whole group anchor chart to help students gain familiarity.
As you introduce a new concept, add it to your whole group anchor chart, one at a time over several days. You can add examples to your anchor chart for students to reference throughout your unit.
These visual representations will help your learners grow and practice each strategy to find the one that makes the most sense to them.
Each time a subtraction with regrouping strategy is added to the anchor chart, I like to have students add it to their own personal anchor chart that they complete in their math journal. This allows them to take ownership in the process and always have it as a reference.
Subtraction with Regrouping Strategy #1: Base Ten Model
Using hands-on manipulatives will help your students understand how subtraction with regrouping works using the base ten model.
You can use physical base ten blocks, paper drawings, or even craft supplies like pipe cleaners and pom poms or snacks like cheese crackers and pretzel rods.
Place Value Mats
I like to give students a place value mat to practice this strategy and represent the minuend and the subtrahend. The steps for modeling subtraction with regrouping using the base ten strategy are easy!
- Build the minuend with base ten blocks.
- Subtract the ones first. Ask your students, “do you need to regroup?”
- Exchange a tens block for ten ones.
- Subtract the ones and then the tens to solve for the difference.
Place Value Interactive Notebook Activity
I recommend practicing this same strategy using a pencil and paper to give students further practice and connection to the concept.
Your students will always have access to paper and pencil, but may not always have base ten blocks, so it is important for them to know how to use this strategy in both ways.
The example below shows this being done using a Draw It! Solve It! interactive journal activity.
3-Digit Place Value Subtraction Cards
Once your students master 2-digit subtract using the base ten model, they may be ready to try 3-digit subtraction. Your students will now be using hundreds, tens, and ones, and will need to be more clear on the concept of place value.
Try using subtraction cards to practice 3-digit subtraction with regrouping. These simple steps will lead your young mathematicians to finding an answer and understanding the why behind the process.
To use the 3-digit place value subtraction cards:
- Mix up the subtraction cards and place them in a stack in front of you.
- Draw the top card and build the minuend using place value blocks or other fun manipulatives. The example shows paper squares to represent the hundreds, pipe cleaners for the tens, and small pom poms for the ones.
- Take away the subtrahend and look at the ones. Ask your students, “do you need to regroup?” Take away the tens. Ask again, “do you need to regroup?” Subtract the hundreds. Solve for the difference.
- Write the answer on the recording sheet.
Subtraction with Regrouping Strategy #2: Expanded Form Method
If your students understand the base ten model and using place value with regrouping strategies, the next method to share is using the expanded form method. This subtraction with regrouping strategy breaks both the minuend and subtrahend apart to show the value of the tens and the ones in each number.
Here is how the expanded form strategy works using the example 53-17:
- Expand both numbers. (53 → 50 + 3, 17 → 10 +7). Ask your students, “can you subtract the ones?” If not, guide them to regroup.
- Exchange a 10 and add it to the ones.
- Subtract and solve for the difference. (40-10 = 30, 13-7 =6 → 30+6 =36).
Expanded form helps students grow their knowledge of place value to really understand how tens and ones (and hundreds with three digit subtraction with regrouping) work.
Subtraction with Regrouping Strategy #3: Number Line Strategy
Open number lines are a visual strategy where students use large hops to represent the tens place and small skips to represent the ones place. The subtraction with regrouping strategies bundle shares problems and examples that allow your students to draw out and reflect on the why of this problem solving method.
Use these steps to solve a subtraction with regrouping problem using a number line:
- Draw an open number line.
- Write the minuend at the end of the number line.
- Hop backwards (using large hops for tens and small skips for ones) to find the difference.
Number Line Interactive Notebook Activity
Having your students identify how many of each hop they need to draw helps when it comes to actually putting it on paper.
This subtracting on a number line interactive notebook activity is a great way for students to practice this strategy further.
The more comfortable they get with this strategy, the faster they’ll become and the more confident they’ll be in doing this mentally.
Subtraction with Regrouping Strategy #4: Standard Algorithm
Another subtraction with regrouping strategy is the standard algorithm. If you open up your old 2nd grade math book, this is probably the algorithm you’ll see. This method focuses a little less on the why, but it is still an effective way to share how to subtract with regrouping.
Here is how the standard algorithm strategy works using 45-27=18:
- Start with the ones place. If the number on the bottom is larger, regroup.
- Exchange a ten for ten ones. Remember the rhyme, more on the floor? Go next door and get ten more!
- Subtract and solve!
Here is how the standard algorithm strategy works using 45-22=23:
- Start with the ones place. More on top? No need to stop!
- Subtract and solve!
Here is how the standard algorithm strategy works using 45-25=20:
- Start with the ones place. Numbers the same? Zeroes the game!
- Subtract and solve!
Subtraction with Regrouping Strategy Flipbook
At the end of your unit, review each subtraction with regrouping strategy with a subtraction with regrouping flipbook! These flipbooks are fun, hands-on, and are a great way to review these 4 strategies. Students can keep them to use as a reference later on.
Using Word Problems
No matter what method your students use, word problems allow them to demonstrate their knowledge through real life application.
The subtraction with regrouping strategies unit for 2nd grade will give you word problems to share in small groups, whole group instruction, and independent practice with your students.
These subtraction with regrouping strategies will allow your 2nd grade students to reach standards and understand the why behind two and three digit subtraction with regrouping!
Here are some resources that you may find helpful:
Subtraction with Regrouping: This guided math unit includes 2 weeks worth of lesson plans to teach two-digit and three-digit subtraction with regrouping in 2nd grade. There are activities for whole group lessons, independent practice, and small group instruction. The activities include a lot of hands-on practice with manipulatives, interactive notebook activities, and math stations to use all year long.
Regrouping Task Cards: This is a set of task cards that includes addition and subtraction word problems.
If you are looking for strategies for teaching addition and subtraction without regrouping, check out the blog posts below.
Are you looking for addition with regrouping strategies? Check out this blog post for them.
Check out my Subtraction with Regrouping Strategies YouTube video below.
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