1st Grade · Operations & Algebraic Thinking
1.OA.A.1: Use addition and subtraction within 20 to solve word problems
1.OA.A.1 is a 1st 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 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
In plain words
Use addition and subtraction within 20 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
I had some toy cars. My friend gave me 3 more cars. Now I have 8 cars in total. How many toy cars did I have at first?
- 3
- 5
- 8
Where students can get stuck
- Adding every number out of habit, answering 20 instead of 4 for "Sam has 12 grapes and eats some. Now he has 8."
- Treating "more" as a signal to add, answering 12 instead of 6 when Lia's 9 shells are 3 more than Ben's.
- Losing track when drawing a story, mixing up which dots belong to which group and counting some of them twice.
Effective teaching strategies
- Act out a story with counters, such as 12 counters with some pushed away until 8 remain, and have students write 12 − ? = 8 for what happened.
- Pair two stories that both say “more” but need different operations, such as Lia's 9 shells being 3 more than Ben's, and Ben's shells being 3 more than Lia's 9, and have students draw each.
- Ask students to label every part of a drawing with its number or a question mark, so they track which dots belong to which group and where the unknown sits.
Units that teach this standard
Find where 1.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
Saxon Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Adding and subtracting story problems within 20 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.