1.OA.B.3
Apply properties of operations as strategies to add and subtract. Students need not use formal terms for these properties. Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. (Commutative property of addition.) To add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. (Associative property of addition.)
Students will be given 3 + 8 = 11 and tasked with 8 + 3 = __. They should also solve missing number problems. For example, given 2 + 7 = 9, task them with 7 + __ = 9.