1. Applying the Traditional Algorithm
Unit of Study 6: Using Algorithms for 2-Digit Addition and Subtraction
Global Concept Guide: 4 of 4

2. Content Development
This GCG is a culmination of all of two digit addition and subtraction.
Students will need to be somewhat fluent in most of the strategies introduced from Units 4 and 5.
Throughout all of this GCG remind students of their basic facts as they are solving problems.

3. Words and Phrases to Avoid!
Borrow
Carry
Knock on your neighbor’s door
Go get some sugar from you neighbor
Bigger bottom, better borrow!
You can’t take a bigger number from a smaller number
Each of these words and phrases create misconceptions and hinder students from understanding the mathematics involved in the algorithm. Use the following words instead:
Regroup
Exchange
Trade

4. Day 1
Use lesson 4.10 to guide your lesson from today. Students will need to solve addition and subtraction problems with unknowns in all positions.

5. Day 2 & 3
Days 2and 3 should be focused on students solving multi-step word problems.
Word problems should mirror those in lesson and the multi-step problem document in your GCG. While these problems are awesome to use, you may want to change the names to match those of your students!
It would be important to have a deep discussion about how challenging these problems are. This would be a great time for you to revisit/reread the “Disequilibrium” article.
These two days are a targeted focus on SMP 1. Students should not be told what operation to use, but they should rely on visualizing to understand how to solve the problem.