2nd Grade · Number & Operations in Base Ten
2.NBT.B.6: Add up to four two-digit numbers
2.NBT.B.6 is a 2nd 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
Add up to four two-digit numbers using strategies based on place value and properties of operations.
In plain words
Add up to four two-digit numbers.
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 5 + 5 + 5 + 5 + 5?
- 20
- 25
- 30
Where students can get stuck
- Leaving out one of the numbers partway through, especially with four, so the total comes out short.
- Forgetting to regroup when the ones make more than 9, writing all of 15 in the ones place.
- Adding strictly left to right and missing easy pairs, such as 36 and 14 making a friendly 50.
Effective teaching strategies
- Ask students to circle two numbers in a list whose sum is a multiple of ten, such as 23 and 47 making 70, and add that pair first.
- Have students add the tens digits and the ones digits separately, such as 4 + 1 + 8 + 6 = 19 ones in 24 + 31 + 18 + 26, then trade 10 ones for a ten.
- Model crossing off each addend as it joins the running total, then let students do the same, so no number is left out of a list of three or four.
Units that teach this standard
Find where 2.NBT.B.6 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
Reveal Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Adding up to four two-digit numbers 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.