Properties of Addition Chapter 2-1

Mental Math Answering math problems without a calculator or pencil and paper.

Communicative Property Add two numbers in any order –Example 17+9= = 26

Associative Property You can change the grouping of any numbers. –E–Example = = = = 20

Grouping Number Find compatible numbers: –E–Easy to add mentally. Numbers that add up to a number with a zero at the end Example: 10, 20, 30

Examples of Compatible Numbers

How It Works Communicative Property: Change the order 17 + (9+3) = (9+3) + 17 Associative Property: Change the grouping 17 + (3+9) = (17 + 3) + 9

Solve It (17 + 3) = = 20 29

= = = 20 86

= = =

= = = 50 77