Math is not taught the same way it was when we were kids, and that’s not necessarily a bad thing! Before students learn subtraction with regrouping strategies, for example, they should know the why behind the math. That’s the difference in today’s math. It’s all about problem solving and knowing the reasons behind the strategies and operations.
Because not all students learn the same way, I like to share multiple strategies with my students when it comes to subtraction with regrouping.
Display anchor charts.
Learning the four subtraction with regrouping strategies will be new for many of your students. Share examples on anchor charts you can refer to throughout your unit. These visual representations will help your learners grow and practice each method to find what makes the most sense to them. Each strategy is introduced one a time over several days.
Each time a subtraction strategy is added to our anchor chart, I have my 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.
Base Ten Model
Using manipulatives will help your students understand how subtraction with regrouping works using the Base Ten Model. Use physical blocks or paper drawings to represent the minuend and the subtrahend. The steps 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.
I recommend practicing this same strategy using a pencil and paper. Your students will always have access to these supplies but they won’t always have base ten blocks so it is good for them to know. The example below shows this being done using a journal activity from my Subtraction with Regrouping Unit.
Once your students master two-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 three-digit subtraction with regrouping. These simple steps will lead your young mathematicians to finding an answer and understanding the why behind the process.
- 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.
If your students understand the base ten model and using place value with regrouping strategies, the next method to share is using expanded form. 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.
Try it with 53-17.
- Expand both numbers. (53 → 50 + 3, 17 → 10 +7). Can you subtract the ones? If not, 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 the knowledge of place value to really understand how tens and ones (and hundreds with three digit subtraction with regrouping) work.
Number Line Strategy
Number lines are a visual strategy where students use large hops for tens places and small skips for ones. 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 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, tens, and small skips, ones) to find the difference.
Having your students identify how many of each hop they need to draw helps when it comes to actually putting it on paper.
Another subtraction with regrouping strategy is the standard model. Open up your old second grade book, and 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 strategies.
Example: 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. Get ten more!
More on top? No need to stop.
Example: 45-25 = 20
Numbers the same? Zeroes the game!
Use 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 bundle will give you word problems to share in small groups, whole class instruction, or independent practice with your students.
These subtraction with regrouping strategies will allow your second grade students to reach standards and understand the why behind two and three digit subtraction with regrouping! Try these activities in the ready-to-go bundle today!
Are you looking for addition with regrouping strategies? Check out this blog post for them.