1. Adding and Subtracting Decimals 1-2

2. Adding Decimals Align the decimal points Insert zeros so each addend has the same number of decimal points Example: Find 2.31 + 19.1 + 1.882 2.310 19.100 + 1.882 ________ 23.292

3. Subtracting Decimals Align the decimal points Regroup if necessary Subtract To subtract a decimal from a whole number, place a decimal point after the whole number, and align the decimal points. Annex as many zeros as needed to have the same number of decimal points

4. Properties of Addition Identity Property of Addition The sum of zero and a is a. Arithmetic: 5.6 + 0 = 5.6 Algebra: a + 0 = a Commutative Property of Addition Changing the order of the addends does not change the sum. Arithmetic: 1.2 + 3.4 = 3.4 + 1.2 Algebra: a + b = b + a

5. Properties of Addition Associative Property of Addition Changing the grouping of the addends does not change the sum Arithmetic: (2.5 + 6) + 4 = 2.5 + (6 + 4) Algebra: (a + b) + c = a + (b + c) Example: Find 0.7 + 12.5 + 1.3 0.7 + 1.3 + 12.5Commutative Prop. (0.7 + 1.3) + 12.5Associative Prop. 2 + 12.5 = 14.5