2-1: Addition Properties Today we will learn… How the 3 properties of addition can help us add together groups of numbers. 2-1: Addition Properties Vocabulary Addends Sum Commutative property Associative Property Identity Property

2 + 5 = 7 Vocabulary Addends Sum The addends are all of the numbers that you are adding together. The sum is the answer to an addition problem.

Commutative Property of Addition The commutative property of addition tells us that no matter what order you add two numbers in, the answer will always remain the same. Example: 2 + 5 = 5 + 2. Both problems have the answer of 7. Can you write an example of the commutative property? Demonstrate to students with counters in cups the property of addition. First add the first cup then the second. Then change the order of the cups and add them again. Count the counters in front of the students and have them tell you that the answer stayed the same no matter what order you added the cups in.

Poetry Time! The flip flop property Is lots of fun It means 1 + 2 Equals 2 + 1 Let’s try a flip flop! See, 2 + 8 Equals 8 + 2 10! Isn’t that great?

Associative Property The Associative Property of Addition states that when you add three or more numbers, you can add them in any order and the answer will stay the same. Example: (3 + 2) + 1 is the same as 3 + (2 + 1). No matter what order you add the numbers in, both will equal 6. Is (2 + 4) + 3 equal to 2 + (4 + 3)? You can demonstrate this problem with counters as well. Use either real counters or the EnVisions online counters to show.

Identity Property of Addition The Identity Property of Addition states that the sum of any number plus zero will be the number itself. Examples: 7 + 0 = 7 289 + 0= 289 243,981 + 0 = 243,981

Let’s Review the Properties Watch this song to help you remember what each of the properties tell us about addition: Addition Properties Song!

NAME THAT PROPERTY! Tell which property each example models. 4 + 2 = 2 + 4 98 + 0 = 98 5 + (4 + 7) = (5 + 4) + 7 657 + 0 = 657 (8 + 4) + 5 = 8 + (4 + 5)

FILL IN THE MISSING NUMBER Complete the number sentence by filling in the blanks. Tell which property is being demonstrated. 77 + 34 = 34 + ___ 8 + (2 + 5) = (8 + __) + 5 453 + ___ = 700 + 453 98 + ___ = 98 7 + (3 +__ ) = (7 + __) + 9 0 + ___ = 43

Problem Solving Carefully read the problem. Underline the question. [Bracket] important words and numbers.  Eliminate unnecessary information.   Solve and check your work. A Lionfish has 13 spines on its back, 2 spines on the middle of its underside, and 3 spines near its tail. How many spines does a lionfish have in all? What property shows that you can add the numbers in any order?