Kindergarten · Number & Operations in Base Ten
K.NBT.A.1: Compose and decompose numbers 11-19
K.NBT.A.1 is a kindergarten 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
Compose and decompose numbers from 11 to 19 into ten ones and some further ones, e.g., by using objects or drawings, and record each composition or decomposition by a drawing or equation (e.g., 18 = 10 + 8); understand that these numbers are composed of ten ones and one, two, three, four, five, six, seven, eight, or nine ones.
In plain words
Compose and decompose numbers 11-19.
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 do 10 and 1 make?
- 10
- 11
- 12
Where students can get stuck
- Thinking the 1 in 16 means one object, so they show 16 with 1 block and 6 blocks.
- Losing count while building the ten, so the group of ten ends up holding 9 or 11 objects.
- Writing 13 = 10 + 3 but not 10 + 3 = 13, or not linking the equation to the objects.
Effective teaching strategies
- Draw a ten-frame on large paper, fill it with 10 large circles or blocks, add 3 more outside it, and have students say “ten and three” before they say thirteen.
- Have students circle exactly ten objects in a drawing of 16 and say that the 1 in 16 means this group of ten, not one object.
- Write 13 = 10 + 3 beside the picture and also 10 + 3 = 13, and have students point to the part of the picture that matches each number.
Units that teach this standard
Find where K.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
Everyday Mathematics
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Reveal Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Teen numbers as ten and some more 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.