3rd Grade · Number & Operations in Base Ten
3.NBT.A.3: Multiply by multiples of 10, like 4 × 70 = 280
3.NBT.A.3 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
Multiply one-digit whole numbers by multiples of 10 in the range 10-90 (e.g., 9 x 80, 5 x 60) using strategies based on place value and properties of operations.
In plain words
Multiply by multiples of 10, like 4 × 70 = 280.
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
3 × 90 is the same as 3 groups of 9 tens. How many tens is that in all?
- 12 tens
- 27 tens
- 270 tens
Where students can get stuck
- Multiplying the digits and forgetting the tens, writing 4 x 70 = 28 instead of 280.
- Writing the wrong number of zeros when the fact already ends in zero, so 5 x 80 becomes 40 or 4,000 instead of 400.
- Using the add-a-zero trick without knowing why, so they cannot tell whether 3 x 60 = 180 is reasonable.
Effective teaching strategies
- Connect 4 × 70 to 4 × 7 tens, so students see the answer is 28 tens, or 280.
- Ask students to find 5 × 80 as 5 × 8 tens, and explain why the answer is 400 and not 40 even though 5 × 8 = 40 already ends in a zero.
- Ask students to explain why 3 × 60 = 180 is reasonable by comparing it with 3 × 6 = 18 and with 3 × 100 = 300.
Units that teach this standard
Find where 3.NBT.A.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
Eureka Math²
Everyday Mathematics
i-Ready Classroom Mathematics
Illustrative Mathematics
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Multiplying by tens, like 4 x 70 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.