Examples: 5 + 4 = 9, so 9 – 4 = 5 3 x 4 = 12, so 12 ÷ 4 = 3 Inverse Operations Opposite operations that undo each other; addition and subtraction are inverse operations; multiplication and division are inverse operations Examples: 5 + 4 = 9, so 9 – 4 = 5 3 x 4 = 12, so 12 ÷ 4 = 3

Variable A letter or symbol that stands for one or more numbers Example: 4 + j = variable

– A number sentence that uses an equal sign to show that two amounts are equal. Some equations have variables Equation 7+3=10 an equation 7+n=10 an equation with a variable

Fact Family – A group of facts that share the same numbers and use inverse operations Fact Families can be addition and subtraction. The 6, 3, 9 Family 6+3=9 3+6=9 9-6=3 9-3=6

Fact families can also be multiplication and division. The 5, 2, 10 family 5x2=10 2x5=10 10÷5=2 10÷2=5