3rd Grade · Number & Operations in Base Ten
3.NBT.A.1: Round numbers to the nearest 10 or 100
3.NBT.A.1 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
Use place value understanding to round whole numbers to the nearest 10 or 100.
In plain words
Round numbers to the nearest 10 or 100.
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 43 rounded to the nearest 10?
- 50
- 40
- 30
Where students can get stuck
- Looking at the wrong digit, such as checking the 7 when rounding 347 to the nearest hundred and getting 400.
- Changing the rounded digit but keeping the digits after it, so 347 rounded to the nearest ten becomes 357.
- Rounding every number that ends in 5 down, such as 65 to 60, unsure which way the halfway point goes.
Effective teaching strategies
- Place the number on a number line between two tens or two hundreds, and ask which one it is closer to.
- Ask students to circle the digit they are rounding to and underline the digit to its right, then explain what the underlined digit tells them.
- Show 65 exactly halfway between 60 and 70 on a number line, and explain that people agree to round a halfway number up to 70.
Units that teach this standard
Find where 3.NBT.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
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
Families can read Rounding to the nearest 10 or 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 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.