2nd Grade · Operations & Algebraic Thinking
2.OA.C.3: Determine whether a group of objects (up to 20) has an odd or even number of members
2.OA.C.3 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
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 express an even number as a sum of two equal addends.
In plain words
Determine whether a group of objects (up to 20) has an odd or even number of members.
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
Is 16 an even or odd number?
- Even
- Odd
- Neither
Where students can get stuck
- Judging odd or even by size, thinking a large number like 18 must be odd or every small number is even.
- Pairing objects but skipping one or counting a pair twice, so a group of 10 looks odd.
- Writing an even number as any two addends, such as 12 = 5 + 7, rather than as a double like 6 + 6.
Effective teaching strategies
- Have students line up linking cubes in two columns, one partner for each cube, and say whether one is left over, so odd and even come from pairing and not from size.
- Count a group of 10 cubes by 2s, touching one pair for each number said, and ask what would be different if 11 cubes were counted the same way.
- Ask students to write an even number as a double, such as 14 = 7 + 7, and explain why 14 = 5 + 9 does not show two equal addends.
Units that teach this standard
Find where 2.OA.C.3 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 Odd and even numbers 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.