Kindergarten · Counting & Cardinality
K.CC.A.1: Count to 100 by ones and by tens
K.CC.A.1 is a kindergarten Common Core math standard in Counting & Cardinality. 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
Count to 100 by ones and by tens.
In plain words
Count to 100 by ones and by tens.
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
Which number comes between 7 and 9?
- 10
- 6
- 8
Where students can get stuck
Count to 100 by ones.
- Getting stuck at the end of a ten, saying "twenty-nine, twenty-ten" instead of thirty.
- Skipping a number partway through a ten, such as going from 56 straight to 58, without noticing the gap.
- Saying "fiveteen" for fifteen or "threeteen" for thirteen, since those teen words don't sound like the numbers they come from.
Count to 100 by tens.
- Counting by tens past ninety to "ten-ty," not yet knowing that one hundred comes after 90.
- Mixing up words that sound alike, such as saying fifteen for fifty or sixteen for sixty while counting by tens.
- Sliding back into counting by ones partway, so 10, 20, 30 turns into 31, 32, 33.
Effective teaching strategies
- Pause at 29, 39, and 49 while the class counts by ones, and say the next number together, so students hear that thirty follows twenty-nine.
- Point to the last column of a hundred chart as students count by tens, so they see that 100 comes right after 90.
- Say pairs such as fifteen and fifty slowly, stressing the -teen and -ty endings, and have students repeat each so they hear the difference.
Units that teach this standard
Find where K.CC.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
Into Math
Math Expressions
Reveal Math
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 counting 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.