Number
and Operations in Base Ten

Represent and solve problems involving addition and subtraction.

1.OA.1

Use addition and subtraction within 20
to solve word problems involving situations of adding to, taking from,
putting together, taking apart, and comparing, with unknowns in all
positions, e.g., by using objects, drawings, and equations with a symbol
for the unknown number to represent the problem.

Understand and apply properties of operations and the relationship
between addition and subtraction.

1.OA.3

Apply properties
of operations as strategies to add and subtract. 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.)

1.OA.4

Understand subtraction
as an unknownaddend problem. For example, subtract 10 – 8 by finding the
number that makes 10 when added to 8.

Add and subtract within 20.

1. OA.5

Relate counting
to addition and subtraction (e.g., by counting on 2 to add 2).

1.OA.6

Add and subtract
within 20, demonstrating fluency for addition and subtraction within 10.
Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 =
10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3
– 1 = 10 – 1 = 9); using the relationship between addition and subtraction
(e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating
equivalent but easier or known sums (e.g., adding 6 + 7 by creating the
known equivalent 6 + 6 + 1 = 12 + 1 = 13).

Work with addition and subtraction
equations.

1.OA.7

Understand the meaning of the equal sign, and determine if equations
involving addition and subtraction are true or false. For example, which of
the following equations are true and which are false? 6 = 6, 7 = 8 – 1, 5 +
2 = 2 + 5, 4 + 1 = 5 + 2.

1.OA.8

Determine the unknown whole number in an addition or subtraction
equation relating three whole numbers. For example, determine the unknown
number that makes the equation true in each of the equations 8 + ? = 11, 5 = – 3, 6 + 6 = .
