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1st Grade · Math · Domain guide

Operations & Algebraic Thinking in 1st Grade (1.OA)1.OA Standards

Short answer. First grade is the year addition and subtraction stop being a counting trick and start being a system. The 1.OA standards push the numbers up to 20, bring in word problems where the unknown can sit anywhere (5 + ? = 9, not just 5 + 4 = ?), and introduce strategies like counting on, making ten, and using a known fact to find a new one. By year's end, sums and differences within 10 should come quickly.

Four clusters organize the domain: 1.OA.A is solving word problems, including ones with three numbers; 1.OA.B is the properties, like knowing 8 + 3 = 11 means 3 + 8 = 11 too; 1.OA.C is fluency and strategy work within 20; and 1.OA.D is equations, including what the equal sign really means. That last one trips up more kids than you'd guess. Many think = means 'the answer comes next.'

Grade
1st Grade
Learning level
Subject
Math
Skill area
Standards
8
Skills in this domain
Clusters
4
Related skill groups

Complete domain directory

Every 1.OA standard, in order

Open a code for the official wording, a plain-English answer, what the skill can look like at home, and simple activities. The list below follows the Common Core sequence.

01
Cluster

Represent and solve problems involving addition and subtraction.

2 standards

  1. 1.OA.A.1Solve Addition and Subtraction Word Problems (1.OA.A.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.

  2. 1.OA.A.2Add Three Numbers in Word Problems (1.OA.A.2)

    Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

02
Cluster

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

2 standards

  1. 1.OA.B.3Use Addition Properties to Add and Subtract (1.OA.B.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.)

  2. 1.OA.B.4Subtraction as a Missing-Addend Problem (1.OA.B.4)

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

03
Cluster

Add and subtract within 20.

2 standards

  1. 1.OA.C.5Count On to Add and Count Back to Subtract (1.OA.C.5)

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

  2. 1.OA.C.6Add and Subtract Within 20 With Fluency (1.OA.C.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).

04
Cluster

Work with addition and subtraction equations.

2 standards

  1. 1.OA.D.7Understand the Equal Sign: True or False? (1.OA.D.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.

  2. 1.OA.D.8Find the Missing Number in an Equation (1.OA.D.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 = _.

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More than a standards list

Use the framework guide for context, the learning hub for explanations, or printable practice when your child is ready to work on a skill.

1.OA is part of the Common Core State Standards. Whizki keeps official wording separate from parent-friendly explanations.

All Common Core parent guides

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