3 Digit Addition Break Apart Strategy
Students should be exposed to many different strategies when learning how to add 3-digit numbers. The addition break apart strategy is helpful for students to visualize numbers broken apart into hundreds, tens and ones. This strategy is sometimes called the partial sums strategy.
This strategy is perfect to introduce after students master addition using base ten blocks. Students still need practice visualizing place value, but no longer need to see it as base ten blocks. The standard 2.NBT.7 uses many different strategies to master 3-digit addition and subtraction. I take it very slowly to help with mastery of this standard.
Keep reading to learn more about the break apart or partial sums strategy and to find a resource you can use right in your classroom to teach 3-digit addition without regrouping using the break apart strategy.
3 Digit Addition Break Apart Strategy without Regrouping Example
What do you think you would do to start solving 162 + 225 using the break apart strategy?
You would break apart the numbers into hundreds, tens and ones just like you would when writing numbers in expanded form.
In this example, 162 would be 100, 60 and 2.Â
225 would be 200, 20 and 5.
To help the students visualize, they will write the numbers in boxes below the problem. It’s important to set up the problems for the students from the beginning.
Once the students start to feel comfortable with the strategy, you can have them draw their own boxes to show their thinking.
Be careful with this step! Many students will want to write 1 instead of 100, 6 instead of 60, 2 instead of 200, and 2 instead of 20. This will impact their thinking later on, so be sure to correct that misconception as soon as you notice it.
Once the numbers are broken apart correctly into their place values, students are ready to add. Start with adding the ones. Have students show their thinking by writing the number sentences below the boxes.
2 + 5 = 7
Note: Some students will want to keep the numbers in their heads instead of writing on paper. Encourage students to show their work throughout every step.Â
Once they start working with larger numbers or use numbers that regroup, it will be easier to make mistakes if they don’t show their work.
Then add the tens. Again, write this number sentence below the boxes.
60 + 20 = 80
The last step is to add the hundreds. Again, write this number sentence below the boxes.
100 + 200 = 300
You are ready to add all the sums together. Continue showing your work by writing this number sentence.
300 + 80 + 7 = 387
Write the final answer in the circle. I encourage my students to always write the final answer in the circle so I know they have completed every step.
This strategy is called break apart since you are breaking apart the numbers into their place value to add.
It can also be called partial sums because you are getting part of the sum each time you add the numbers in different place values.
You can use both names to reference this strategy. In fact, it is important to share this with students so you don’t hear them tell you they don’t know what the strategy means if it is referenced on a standardized test! They do know what to do!
Break Apart 3 Digit Addition without Regrouping Practice
Do you need some practice pages for your students to use with this strategy?
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