1. Regrouping Ones, Tens and Hundreds with the Traditional Algorithm Unit of Study 7: 3-digit Addition and Subtraction Global Concept Guide: 3of 5

2. Content Development  Slow and steady wins the race. Keep in mind students should be stronger in all the place value/ invented strategies for adding and subtracting than the traditional algorithm.  The standards documents linked on the Unit of Study state that students are not required to MASTER the traditional algorithm until the end of 4 th grade. This means they will still be introduced to the strategy, but the focus should remain on place value strategies.  Keep in mind not to build misconceptions with vocabulary. Teachers should be focusing on SMP 6 with precision of vocabulary and meanings of procedures throughout all of this unit.  Students are only adding and subtracting to 1000 NOT through the thousands place. This is a change from the NGSSS standards.

3. Day 1  Day 1 is focusing on problems involving regrouping tens for both addition and subtraction.  Pull specific problems noted in the GCG from lessons 6.3, 6.4 and 6.7.  It is vital to give students opportunities to visualize problems to determine the operation they should use.  Students should have the opportunity to solve these problems with base ten blocks. You may find many students are ready to draw pictures of the models to solve the problems. This is a natural and appropriate step.

4. Day 2  Lessons 6.8 and 6.9 should be used to help focus the day on regrouping hundreds.  Keep in mind, when adding, students should not solve problems that involve a sum greater than 1000.  Continue to ask questions about the value of numbers as you did when adding two digit numbers. Once students have made all their trades, the teacher should ask, “Does 1 hundred, 9 tens and 13 ones have the same value of 213?”

5. Day 3  Day 3 should be focused on students specifically connecting the actions they are taking when regrouping ones, tens and hundreds with base ten blocks to the traditional algorithm.  Teachers can use a variety of problems from lessons 6.3-6.5 to ensure students understand the procedure of the traditional algorithm.  Have students make connections between 2 digit regrouping throughout this unit.

6. Day 4  Components from lesson 6.8 should be used to guide today’s lesson. Students should be using base ten blocks and/or pictures to regroup their models and connect their actions to the traditional algorithm.  Focus your questioning today like those posed on Day 2 of this GCG to ensure students understand the connection to representing numbers flexibly and equal values of numbers.

7. Day 5  Students should be exposed to addition and subtraction problems today. Throughout the day, your focus should be on how the traditional algorithm works.  Students should be able to articulate how regrouping numbers does not change the value of the numbers involved. The only time the value of their number changes is when something is added to it or taken from it.  While students are solving problems, point to any number and ask, “What is the value of this number? What does it represent in the problem?” This is a great way for students to contextualize. (SMP 2)

8. Enrich/Reteach/Intervention  To enrich students, have problems similar to those on TE p. 289B with missing digits in problems. Use riddles similar to those on TE p. 312B (both enrich sections)  For reteach ideas, see Online Resources. Students can be assigned to mini-lessons through Think Central.