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Common Core Math2nd GradeOperations & Algebraic Thinking

2.OA.4: Add Up the Rows of an Array

Also written as 2.OA.C.4 and CCSS.MATH.CONTENT.2.OA.C.4 · Cluster: Work with equal groups of objects to gain foundations for multiplication.

Make an Array WorksheetAll 26 2nd Grade Math Standards

The Official Wording

Use addition to find the total number of objects arranged in rectangular arrays with up to 5 rows and up to 5 columns; write an equation to express the total as a sum of equal addends.

Common Core State Standards, Grade 2, Operations & Algebraic Thinking · Read it at the source · Checked October 14, 2026

What 2.OA.4 Means in Plain English

Second graders look at rows and columns of objects, up to 5 by 5, and find the total by adding the rows: 3 rows of 5 tulips is 5 + 5 + 5 = 15. Adding the five columns of 3 instead gives the same total.

The equation matters as much as the count: 5 + 5 + 5 = 15 says the rows are equal, which is what 3 × 5 will mean next year (3.OA.1). Arrays also set up area: a rectangle split into rows and columns of squares (2.G.2, then 3.MD.7).

2.OA.4 I Can Statements

  • I can find the total in an array by adding the rows.
  • I can write an equation with equal addends for an array.
  • I can draw an array to match 4 + 4 + 4.

2.OA.4 Worked Example

Three rows of five, read as a sum of equal addends, the way an array gets read before anyone says “times”.

3 groups of 5
Three rows, five dots in each row. Add the rows: 5, 10, 15. Turn the page sideways and it is five rows of three: 3 + 3 + 3 + 3 + 3 is 15 as well.
5 + 5 + 5 = 15

The class garden has 3 rows of tulips with 5 in each row. Each row is one addend, so 5 + 5 + 5 = 15 tulips. Three equal addends, one for each row, and a total of 15.

Common Mistakes with 2.OA.4

Counting every dot by ones

1, 2, 3 ... 15, with no equation written

Try this: Cover all but one row and ask how many. Then uncover the rows one at a time, saying 5, 10, 15, and write each addend.

Adding rows and columns together

3 + 5 = 8 for a 3 by 5 array

Try this: Trace one row with a finger and ask how many dots it holds, then how many rows there are. The addends are all the same.

Unequal addends for an array

5 + 5 + 4 = 14 after losing a dot in the last row

Try this: Have the student draw a line under each row before adding, then count the dots in every row to confirm they match.

Where 2.OA.4 Fits

Comes Before1.OA.2Add three whole numbers, like 4 + 4 + 4, in a word problem.2.OA.3Write an even number as two equal addends.
Alongside2.G.2Split a rectangle into rows and columns of equal squares and count them.2.NBT.2Skip-count by 5s, which is the count for five-dot rows.
Comes Next3.OA.1Read 3 × 5 as three groups of five, which an array shows directly.3.OA.3Solve multiplication word problems with arrays and equal groups.

Practice 2.OA.4

Math Worksheet GeneratorFree ToolArray sheets at the 2nd grade level: dot arrays up to 5 by 5 with a blank equation under each, and an answer key.Grade 2ArraysAnswer key
Make a Worksheet
Word Problem GeneratorFree ToolStories about rows of chairs, trays of muffins and other equal groups, written so the answer comes from adding equal addends.Grade 2Equal groupsAddition
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Quick Check

  1. An array has 4 rows with 3 dots in each row. Write an addition equation for the total.
  2. Write the equation for 2 rows of 5, then for 5 rows of 2. What do you notice?
  3. Stickers come on a sheet with 5 rows of 4. How many stickers are on the sheet?

2.OA.4: Other Names

2.OA.42.OA.C.4CCSS.MATH.CONTENT.2.OA.C.4

Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved. Official wording from the Common Core State Standards PDFs at corestandards.org, last checked October 14, 2026. The explanation, I can statements, example, mistakes and practice on this page are EMStudio’s own, written beside the official wording. They are not part of the standard.