Teaching 3 Digit Addition Strategies in 2nd Grade | 4 Effective Ways to Tackle This Tricky Concept

Teaching multi-digit addition with regrouping is arguably one of the trickiest tasks as a 2nd grade teacher. Students must have a strong foundational understanding of place value in order to grasp this concept and succeed. In this blog post, I’m sharing 4 effective 3 digit addition strategies along with some of my favorite activities that you can incorporate in your lessons as well! 

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Teaching 3 Digit Addition

Before diving into 3 digit addition with regrouping, make sure your students have a strong understanding of place value. Oftentimes, this means teaching, practicing, and reinforcing place value long after your curriculum has moved on. 

In my classroom, we practice place value almost daily, because it’s just that important! I refuse to move on from our place value unit until my students feel confident in this skill. This is one of those times where you as the teacher know best, and rushing onto the next skill will only make it harder for your students. 

Once your students have mastered the foundational place value skills, begin by introducing addition with regrouping strategies with 2 digit numbers.

Think of this as a stepping stone process: place value→ 2 digit addition with regrouping→ 3 digit addition with regrouping.

Learn more about teaching 3 digit addition with the base 10 strategy in this YouTube video.

3 Digit Addition Strategies

The strategies for teaching 3 digit addition with regrouping are the same for 2 digit addition, just with the extra challenge of adding numbers in the hundreds place. Read on to see how to put these 3 digit addition strategies into practice in your classroom.

#1: Base Ten Strategy

When introducing any concept, always start with concrete (AKA, hands-on) models and activities. This helps students understand the WHY behind the process. The base ten strategy is the first 3 digit addition strategy, and it’s one of my favorites. 

Using base-ten blocks is a great way to incorporate the familiarity of place value into solving addition problems. Plus, you can get creative and use a variety of tools and classroom supplies for base ten blocks, such as snacks and art supplies.

Place Value Addition Mat

On the first day of teaching 3 digit addition strategies, I use a Place Value Addition Mat so students can physically practice manipulating the numbers when solving problems. 

In this example of 104+188, students build out each addend with base ten blocks (or in this case… snacks!). 

Then, they add up the ones first. Since 8+4=12, students see that they need to regroup. They look to see if they can exchange any of their ones for a ten. In this example, they can! They will trade out ten ones for a ten. 

They’ll see that they have 2 ones left, so the sum of the ones place is 2. 

Then they look at the tens place. There are now 9 tens, so the sum of the tens place is 9. Finally, in the hundreds place, there are 2 hundreds, making the sum of the hundreds place 2. 

This leads them to the final answer of 292.

Solve and Match Interactive Notebook Activity

Being able to build out addends and solve using physical base ten blocks is important, but students also need to be able to translate the base ten strategy to drawing it on paper, since they won’t always have manipulatives available to them. 

That’s where I like to use this Solve and Match interactive notebook activity during independent practice. 

Students will follow the same process as before, but by drawing out the addends, adding up each place value, regrouping if the sum is more than 10, and so on. 

#2: Expanded Form Strategy

After teaching the base ten 3 digit addition strategy, move on to the expanded form strategy. If students have a solid understanding of place value and expanding numbers, this can be a very valuable way for them to solve multi-digit addition problems. 

When teaching this 3 digit addition strategy, each addend will be broken apart and expanded to show the value of the hundreds, tens, and ones place. This allows students to visually see the value of each digit.

Expanded Form Work Mat

You can see how this is done using this expanded form work mat and the example 347+265.

1. Expand the first addend. 347 becomes 300+40+7.
2. Expand the second addend and write it underneath. 265 becomes 200+60+5
3. Solve vertically based on place value, starting with the ones, then adding the tens, followed by adding the hundreds. 
4. Solve for the sum.

#3: Number Line Strategy

A super powerful and visual strategy for teaching 3 digit addition is the open number line strategy. With this strategy, students “hop” along a number line to add both 3 digit numbers and solve. I use the phrases hundreds leaps, tens hops, and ones skips.

Students will draw leaps to represent adding 100, large hops to show adding 10, and small skips for adding 1. In the beginning, I have students use base ten blocks on the open number line to help visualize this concept. You can see how this is done in this blog post.

Adding on a Number Line Activity

I like to have students practice the open number line strategy for adding 3 digit numbers in a whole group setting using this Adding on a Number Line interactive notebook activity. I like this because we can work through each example together as I model on the whiteboard and students can always look back in their notebooks to see how this strategy works. 

In this activity, students will write the first addend on the number line and then add by drawing giant 100s leaps, large 10s hops, and small 1s skips until they find the sum.

#4: Standard Model

It may come as a surprise to some, but the standard model for 3 digit addition is actually the last one that should be taught. Again, students need to understand the WHY first, which is what the base ten, expanded form, and number line strategy helps them do. 

Most likely, the standard model is how you learned to add 3 digit numbers with regrouping. 

When teaching this 3 digit addition strategy, I use the saying, “If it’s ten or more, carry next door.”

Addition with Regrouping Practice Activity

In order to help students stay on track when adding, have them highlight the ones column before they begin adding and regrouping. This helps them remember to add the ones place first, then the tens, and finally, the hundreds. This can be tricky for students since they are trained to read left to right, and in this case, it’s backwards. 

You can see how this is done in this 3 Digit Addition with Regrouping practice activity. 

Students will line up the addends vertically, highlight the ones place, and begin adding. If the sum of the ones place is ten or more, they will carry a ten next door. The same goes if the sum of the tens place is ten or more, then they will carry a hundred next door before adding for the total sum.

Rolling Addends

A fun way to practice 3 digit addition using the standard model is with this Rolling Addends game.

Students will pair up and grab a set of Wiz dice. They’ll roll the dice to create both 3 digit addends. Then, they’ll use the standard model to solve.

The player with the largest sum wins the round and gets a tally at the bottom. The player with the most tallies at the end of the game wins!

Free Addition with Regrouping Lesson Plan

Would you like to try a FREE sample addition with regrouping lesson plan from my 2 and 3 Digit Addition with Regrouping guided math unit? Simply fill out the form below and your complete sample lesson plan and materials will be delivered straight to your inbox!

I hope this blog post has helped you feel more confident in teaching 3 digit addition strategies and given you some tools and activities that you can implement in your own classroom. Once your students are familiar with each strategy, they’ll feel more confident and empowered to choose the one that works best for them!

For more 3 digit addition activities and ideas, check out the resources and blog posts below! You can also find more resources in my TPT store.

• How to Teach Addition with Regrouping
• 6 Fun Addition with Regrouping Activities That Follow the CPA Approach
• Free Addition with Regrouping Lesson Plan Using Base Ten Blocks