2nd Grade · Operations & Algebraic Thinking
2.OA.C.4: Use addition to find the total number of objects arranged in rectangular arrays
2.OA.C.4 is a 2nd grade Common Core math standard in Operations & Algebraic Thinking. Here’s what it really covers, and how you can help your students learn it.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
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.
In plain words
Use addition to find the total number of objects arranged in rectangular arrays.
Sample questions from student practice
These questions from Bobby's Math Club are the kinds of questions your students will see. You can try answering them to see what a student might see.
Question 1 of 3
Look at the dots arranged in rows. Which addition sentence shows the total number of dots?
- 4 + 3 = 7
- 4 + 4 + 4 = 12
- 3 + 3 + 3 = 9
Where students can get stuck
- Counting every object one at a time instead of adding rows, then skipping or recounting some in the middle.
- Adding the number of rows to the number of columns, answering 7 for 3 rows of 4.
- Writing the wrong number of addends, such as 4 + 4 for 3 rows of 4, after losing track of the rows.
Effective teaching strategies
- Have students build an array from counters, such as 3 rows of 4, and touch one row at a time while saying the running total 4, 8, 12.
- Ask students to write the repeated-addition equation under each array, such as 4 + 4 + 4 = 12, and point to the row that each addend matches.
- Show an array of 5 rows of 2 and ask why the total is 10 and not 5 + 2, having students point to each row as one equal addend.
Units that teach this standard
Find where 2.OA.C.4 lands in the program you teach. Each unit has a guide written for families. Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence.
Bridges in Mathematics
enVision Mathematics
Everyday Mathematics
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Reveal Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Counting objects in equal rows by adding for a plain-language look at this skill, with three questions to try together and ideas for helping at home.
Help every student practice problem solving at home
In Bobby's Math Club, students practice at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free for every family.
See how it works for teachers
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.