Unit 2: Adding and Subtracting Whole Numbers

Unit 2: Adding and Subtracting Whole Numbers

The main topics of Unit 2 are addition and subtraction of whole numbers, the basic facts and their extensions, solution strategies for solving number stories involving adding and subtracting, and adding and subtracting multi-digit numbers.

Unit 2 Main Areas of Focus:

*To review fact families and number families

*To review and solve “What’s My Rule?” problems

*To use diagrams to help solve number stories

*To review algorithms for adding and subtracting

Daily Lessons:

2.1 Fact Families

2.2 Extensions of Addition and Subtraction Facts

2.3 “What’s My Rule?”

2.4 Parts-and-Total Number Stories

2.5 Change Number Stories

2.6 Comparison Number Stories

2.7 The Partial Sums Algorithm (see below for more information)

2.8 Subtraction Algorithms (see below for more information)

2.9 Addition with Three or More Addends

2.10 Progress Check 2




Subtraction Algorithms

Partial Sums
Partial sums first adds the hundreds, then tens, then ones, and then combines them to get a total.

329
+ 418

300+400= 700

20+10= 30

9+8= 17

747

Trade First
The trade first method is also known as the traditional method. The only difference is that you do all the trading before subtracting.

12 14

3 2 4
+ 1 9 7

12 14

3 2 4
+ 1 9 7

2 3 7

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