1. Strategies for Regrouping Across Zeros
Unit of Study 6: 3-digit Addition and Subtraction
Global Concept Guide: 3 of 4

2. Content Development
Using the strategies in this GCG will help students to be more efficient with subtracting across zeroes. These strategies can be helpful but not forced. Instruction should be differentiated. Students still struggling should still use base-ten blocks.
Keep in mind not to build misconceptions with vocabulary. Teachers should be focusing on SMP 6 with precision of vocabulary and understanding of place value throughout all of this unit.
Students are only adding and subtracting to 1000 NOT through the thousands place.

3. About the Math…

4. Day 1
Essential question: How do you regroup more efficiently when there are zeroes in the number you are subtracting from?
Day 1 is focusing on problems involving regrouping across zeros.
Sample engage problem:
Show students the below pictures. Have students find the value of each picture. How are the representations the same and how are they different? (They all show 200, but in different ways. Some use only hundreds, some use hundreds and tens, and some use hundreds, tens, and ones.)

5. Day 1 continued
Krispy Kreme had 200 chocolate filled doughnuts. They sold 174. How many do they have left to sell? Which representation would be best to use? If we want to use this representation how you record knowing we started with 200 doughnuts. (200 can be thought of as 20 tens. Regrouping 1 ten so we have 19 tens and 10 ones.) Students should understand why this strategy works and be able to represent it with base-ten or quick pics. This will not be effective if they just learn the shortcut.
Additional problems that may be used.
By the end of Day 1, students will be able to regroup more efficiently when there are zeroes in the number they are subtracting from. Sample daily journal questions.

6. Day 2
Essential question: How do we use compensation to subtract across zeroes?
We want students to see how they can use compensation to solve problems. Check out this strategy, Take one, Give one .
This strategy should be modeled first using
base-ten blocks.
Sample engage question:
Five hundred children are enrolled at Apple Elementary. Four hundred twenty-two are at school on Friday. How many are absent?
Additional problems that can be used.
By the end of Day 2, students will be able to
use compensation to help subtract
across zeroes. Possible daily journal questions.

7. Reteach/Enrich/Intervention
If students struggle with this concept, spend more time using base ten blocks to solve the problems and connect it to pictures. Remember, students do not have to show mastery of these strategies.
Enrich
Explain why these zero strategies work in pictures and in words.