3rd Grade · Number & Operations in Base Ten
3.NBT.A.2: Fluently add and subtract within 1000
3.NBT.A.2 is a 3rd grade Common Core math standard in Number & Operations in Base Ten. 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
Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.
In plain words
Fluently add and subtract within 1000.
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 6
What is 245 + 132?
- 113
- 277
- 377
Where students can get stuck
Fluently add within 1000.
- Leaving out the extra hundred when the tens add up to 10 or more, so 352 + 175 comes out as 427 instead of 527.
- Lining up the digits from the left, so 345 + 62 gets added as 345 + 620 and comes out as 965 instead of 407.
- Splitting numbers into hundreds, tens, and ones and then dropping one part, so 238 + 145 adds up to 370 instead of 383.
Fluently subtract within 1000.
- Subtracting the smaller digit from the larger in every column, so 503 - 267 comes out as 364 instead of 236.
- Losing track when the top number has zeros, so 400 - 156 lands on 254 instead of 244.
- Adding when a question asks how many more, so “How many more is 420 than 285?” comes out as 705 instead of 135.
Effective teaching strategies
- Ask students to estimate the sum or difference first, then compare the estimate with their exact answer.
- Use base-ten blocks or place-value drawings to regroup, and have students say each trade out loud, such as 1 hundred for 10 tens.
- Work through subtracting across zeros, such as 400 - 156, by regrouping the hundred into ten tens first and then one ten into ten ones.
Units that teach this standard
Find where 3.NBT.A.2 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
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Each skill has its own guide for families, with a plain-language look at the skill, three questions to try together, and ideas for helping at home.
Help every student practice place value 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.