1. 1-4 6th grade math
Addition Properties

2. Objective
To use addition properties and mental math strategies to compute mentally
Why? To help you add mentally and get a rounded estimate to an addition problem.

3. California State Standards
AF 1.3: Apply … the commutative, associative properties to evaluate expressions … MR 2.0: Use strategies, skills, and concepts in finding solutions.

4. Vocabulary Mental Math Commutative Property Associative Property
The process of producing an exact answer without pencil and paper or other computational aids.
Commutative Property
The order in which numbers are added does NOT affect the sum. (Just which the order.) =
Associative Property
The way in which addends are grouped does NOT affect the sum. (Keep the same order, but switch around the parentheses.)
7 + (11 + 5) = (7 + 11) + 5
Identity Property
The sum of any number and zero (0) is that number.
= 45

5. Vocabulary Compatible Numbers Method
Group together numbers that are easily computed mentally
= ( ) + 68 =
= 158
Break-Apart Method
Break-apart numbers to have easier numbers to work with.
= ( ) + 4 =
= 192
Compensation Method
Change one number to make it easy to use. Then change the other number to compensate (adjust). Imagine a balance.
= ( ) + (16 – 7) =
= 189

6. How to Use Addition Properties
1) Decide whether to use the Compatible Number Method, or Break-Apart Method or Compensation Method 2) Apply the rules to solve either one. 3) Check your work.
Choose a strategy and compute mentally. A) Use the break-apart strategy. = ( ) + 9 = = 83 B) Use the compatible numbers strategy. = (41 + 9) + 55 = = 105

7. Try It! Compatible Numbers = (28 + 32) + 74 = 60 + 74 = 134
2) Compensation Method
= (325 – 5) + ( ) =
= 550
3) Break-Apart Method
= ( ) + 4 =
= 152
4) Compatible Numbers
= ( ) – (79 – 4)
= 120 – 75
= 45
Choose a strategy and compute mentally.

8. Objective Review
To use addition properties and mental math strategies to compute mentally
Why? You can now add mentally and get a rounded estimate to an addition problem. Addition properties and mental math strategies can be used to find exact answers without using pencil and paper.

9. Independent Practice Complete problems 6-17
Copy original problem first.
Show all work!
If time, complete Mixed Review: 18-23
If still more time, work on Accelerated Math.