CCSS.Math.Content.2.OA.C.4
The standard
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 for Mathematics · Operations and Algebraic Thinking
What this standard means
Students need to look at a rectangular array and see equal rows or equal columns. They count the total by adding the same number again and again, then write an equation like 4 + 4 + 4 = 12 or 3 + 3 + 3 + 3 = 12.
Mastery means students can build, draw, count, and write an addition equation for arrays up to 5 by 5. Many students count every object one by one, mix up rows and columns, or write unequal addends. They also may not see that the same array can be described by rows or by columns.
Ways to teach it
- Hands-on activity: Give students counters and grid paper, then call out arrays like 3 rows of 5 for them to build and label.
- Discussion prompt: Show a 4 by 3 array and ask, What addition equation matches the rows, and what equation matches the columns?
- Quick assessment: Display five small arrays and have students write one repeated addition equation for each on a half sheet.
- Real-world connection: Use an egg carton, muffin tin, or classroom tile pattern to write a repeated addition equation for the total spaces.
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Related standards
- CCSS.Math.Content.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, wit...
- CCSS.Math.Content.2.OA.C.3
Determine whether a group of objects (up to 20) has an odd or even number of members, e.g., by pairing objects or counting them by 2s; write an equation to expr...
- CCSS.Math.Content.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 ...
- CCSS.Math.Content.2.G.A.2
Partition a rectangle into rows and columns of same-size squares and count to find the total number of them.