Lesson 2-1 Properties of Numbers

Commutative Properties of Addition and Multiplication Changing the order when you add or multiply does not change the sum or product Examples

Associative Properties of Addition and Multiplication Changing the grouping symbols when you are adding or multiplying does not change the sum or product. Examples

Identity – leaves the value of other numbers unchanged Additive identity 0 is the additive identity, when it is added to a number the number is unchanged Multiplicative Identity 1 is the multiplicative identity, when it is multiplied to a number the number is unchanged

Name each property shown 5 ∙ 7 = 7 ∙ 5 c ∙ 1 = c 7 + a = a + 7 5(xy) = (5x)y

Tip Look for combinations that equal 10 or a multiple of 10, since they are easier in calculating mentally. (4 ∙ 9) ∙ 5 6 + 7 + 14