2nd Grade · Operations & Algebraic Thinking
2.OA.A.1: Use addition and subtraction within 100 to solve word problems
2.OA.A.1 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 and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem.
In plain words
Use addition and subtraction within 100 to solve word problems.
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
What is 80 minus 20?
- 50
- 60
- 70
Where students can get stuck
- Stopping after the first step of a two-step problem and giving the in-between total as the answer.
- Adding whenever a story says "more," even in "Ava has 52 stamps, 17 more than Leo," where Leo has 35.
- Losing track of what each number stands for, then using the wrong amount in the second step.
Effective teaching strategies
- Have students draw a bar or box for each number in the story and write the equation with a symbol for the unknown, such as 8 + ? = 15 or ? - 6 = 9.
- Show a compare story such as “Maya has 40 stickers, 15 more than Sam” as two bars, so students see that Sam has fewer and 40 - 15 = 25 finds his.
- Ask students to reread the question after the first step of a two-step problem and decide whether the number they have answers it yet or only helps with the next step.
Units that teach this standard
Find where 2.OA.A.1 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
Eureka Math
Eureka Math²
Everyday Mathematics
Go Math!
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 One- and two-step story problems within 100 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.