# Properties of Addition Chapter 2-1. Mental Math Answering math problems without a calculator or pencil and paper.

## Presentation on theme: "Properties of Addition Chapter 2-1. Mental Math Answering math problems without a calculator or pencil and paper."— Presentation transcript:

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

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

Associative Property You can change the grouping of any numbers. –E–Example 10 + 7 + 3 = 7 + 3 + 10 = 7 + 3 = 10 10 + 10 = 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 5+5 3+7 6+4 9+1 2+8

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) + 9 17 + 3 = 20 + 9 = 20 29

66 + 18 +2= 18 + 2= 20 + 66= 20 86

64+ 97 + 3= 97 + 3 = 64 + 100 = 100 164

22 + 46 + 4 = 46 + 4 = 22 + 50 = 50 77