# Adding Three-Digit Numbers with Regrouping

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## Objective

SWBAT add three-digit numbers that require regrouping.

#### Big Idea

Students identify, use, and share strategies for adding three-digit numbers that require regrouping.

## Problem of the Day

5 minutes

I write a problem of the day on the board:

135+ 229=

Have students work on their white boards or in their notebooks to solve the problem. I provide students with hundreds, tens, and ones blocks as well as cube manipulatives to use if they want.

Some students may solve this problem by using hundreds, tens, and ones.  Others may solve the problem using an open number line or by using an invented algorithm (i.e: 100 + 30 + 200 + 29).  Others may use column addition and regroup.  Any strategy that yields an accurate answer is appropriate.

## Introduction to New Material

10 minutes

Turn and talk:  What did you do to solve this problem?

After giving students a few minutes to work, I ask two or three students to share the strategies that they used.

Students should be able to discuss how they regrouped and made a new ten. Some students may have drawn hundreds, tens, and ones. If the lowest students are struggling, have one student model how they drew hundreds, tens, and ones to solve this problem.

I give students another problem of the day:  134+ 182=

Have students work on their white boards to solve this problem.

Turn and Talk: What did you do to solve this problem?

It is important in this discussion for students to understand that they regrouped to make another hundred.  If necessary this can be illustrated by drawing tens and ones or by using cubes or place value blocks to model.

NOTE:  In the first problem of the day, students are required to regroup in the tens place.  In the second problem of the day, students are required to regroup into the hundreds place.  This is a new skill for some students--however if students use hundreds, tens, and ones, they will see that regrouping into the hundreds is a similar skill to regrouping into the tens place.

## Guided Practice

10 minutes

I divide students into heterogenous groups of two or three. I give each group one white board (or ask them to come up to the board).  I write a three-digit number sentence on each board.  One member of the team will use the marker to solve the problem while the others will "coach" that teammate.

After one teammate has gone, leave time for feedback and rotate through the rest of the children in each group so that everyone has a chance to be "coached' by their teammates.

Before starting, I talk briefly about good ways to coach like giving friendly tips, saying "I liked the way that you...",  "Make sure that you..." or "Next time you should..."  If students do not have a lot of practice coaching each other it is important to give them sentence stems so that their coaching is meaningful.  Before starting this activity you can model what good coaching looks like by having a student coach you using the sentence stems or by having a student coach another student in front of the class.  Student coaching can be a powerful way to increase achievement and improve accuracy but students need practice to be effective coaches. (MP6)

## Independent Practice

10 minutes

Independent practice is differentiated based on proficiency with this concept (for this skill, err on the side of putting students in lower groups so that they can get enough practice and conceptually understand what regrouping into the hundreds place means).

While students work, I will circulate, starting with group A, then moving to group B, and finally group C.

Group A:  In need of intervention

Students will work on a worksheet that requires regrouping from the ones to the tens (numbers 100-200).  This group will be encouraged to draw hundreds, tens, and ones or use cubes bundled into groups of ten so that they get practice understanding the process of regrouping.

Group B:

Students will work on a worksheet that requires regrouping  from the ones to the tens OR the tens to the hundreds (numbers 100-400). This group will be encouraged to draw hundreds, tens, and ones OR to regroup.

Group C:

Students will work on a worksheet with numbers 100-800 that requires regrouping from the ones to the tens OR the tens to the hundreds (no regrouping into the thousands).  This group will be encouraged to regroup or draw hundreds, tens, and ones.

## Closing

10 minutes

I bring the students back to the rug.

Today we learned how to regroup with numbers in the hundreds. I would like for one of you to model how you solved a problem.

I pick a problem off the worksheet and ask student to model his/her strategy and thinking.

Tomorrow, we will work on word problems that use numbers in the hundreds!