Adding Three-Digit Numbers Without Regrouping

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SWBAT add three-digit numbers without regrouping

Big Idea

Students discover and share strategies for adding three-digit numbers without regrouping.


5 minutes

I am going to write a problem on the board.  I want you to use any strategy that makes sense for you to solve this problem. 

 124+  143=

Work in your notebook (or on a white board to solve this problem).


I allow students to work silently on this problem while I circulate to determine what strategies they are using and what common misunderstandings exist (i.e: some students may be confused by the hundreds place when drawing tens and ones, some students may forget to start adding in the ones place if using column addition). 

Introduction to New Material/ Strategy Share

10 minutes

Now that we have worked on this problem, I want you to turn to your partner and share the strategies that you used to solve!

As students share, I circulate and ask guiding questions:

 What place did you start in (hundreds, tens, ones), and why?  

Show me how this strategy works...

Why did you choose this strategy?

Students may identify that they started in the ones place and added each number.

Turn and Talk (T+T):  How is adding numbers in the hundreds  similar or different from adding numbers that only have two digits?

Students may  identify that they still start in the ones place, that they can still use tens and ones to solve the problem.  They also might identify that they need to draw hundreds or that they also need to add the hundreds place. 

Guided Practice/Group Practice

10 minutes

For guided practice, I divide students into heterogenous groups of two or three. I give each group one white board (or a section of the classroom board). I write a three-digit addition sentence on each board.  One member of the group will use the marker to solve the problem while the other students will "coach" that teammate.

Before allowing groups to start, I spotlight one group and have them model how to do this process.  Make sure that this model group is using kind words, showing support, and giving "tips" to the person who is writing instead of just telling them how to solve the problem. 

I release groups to start and circulate in order to support students and monitor understanding.  After each group does the first problem, I have them pass the white board to a new person in the group and have them work through a second and third problem. 

Independent Practice

10 minutes

Independent Practice is tiered to provide diverse entry points. During independent practice, I will spend the majority of my time with group A (intervention) but will also stop by and check in with group B and group C to see how things are going, identify which strategies students are doing, ask guiding questions, and assist with any students who are having problems. 


Group A: In need of intervention

Students in group A will work on three digit addition problems using numbers 100-300.  They will be encouraged to use whatever strategy works best for them.  Group A will also have place value blocks at their table so that they can use these to more concretely add three digit numbers. 


Group B:  Right on track! 

Students in group B will work on three digit addition problems using numbers 100-500.  They will be encouraged to use whatever strategy works best for them. 


Group C: Extension 

Students in group C will work on three digit addition problems using numbers 100-900.  Some of the problems for group C will include regrouping. They will be encouraged to use whatever strategy works best for them. 

Closing/Exit Ticket

5 minutes

Today we worked together to learn and share strategies for adding three digit numbers.  Some of the strategies we discussed were column addition, drawing hundreds, tens, and ones, and _____________ (any other strategy discussed in your class).   Right now you are going to take what you know and complete an exit ticket.


As students complete the exit ticket, circulate. After students finish, pick up the exit tickets--use these exit tickets to help inform tomorrow's A,B,C groupings for independent work.