Eureka Math² Kindergarten, Module 4: Composition and Decomposition of Numbers to 10
In this unit, your child puts numbers together and takes them apart. Kindergartners find that 8 can be made from 5 and 3 or 6 and 2, use those parts to solve adding and subtracting stories, and work out what goes with a number to make 10. It builds on comparing numbers to 10 and readies your child for the teen numbers, which are ten and some more.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Module 4?
- Putting together and taking apart groups with objects, fingers, and drawings, and writing equations like 8 = 5 + 3. Learn more about showing addition in many ways: Showing addition in many ways · Learn more about showing subtraction in many ways
- Solving put-together and take-apart story problems within 10 by showing what happens with objects or a drawing. Learn more: Adding and subtracting story problems within 10
- Decomposing, or breaking apart, numbers up to 10 into two parts in many ways, such as 8 = 6 + 2 and 8 = 7 + 1. Learn more: Splitting numbers up to 10 into two parts
- Working out what number goes with another to make 10, such as 4 and 6, using fingers or a ten-frame. Learn more: Finding the number that makes 10
- Knowing adding and subtracting facts within 5 quickly, such as 1 + 4 = 5 and 3 - 2 = 1, without counting every one. Learn more about adding fluently within 5: Adding fluently within 5 · Learn more about subtracting fluently within 5
Sample questions to try together
These are real questions from our practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
Start at 7 and hop back 2. Where do you land?
- 2
- 9
- 5
How you can help
- Split 8 socks between two drawers in as many ways as you can, saying each one aloud, such as 5 and 3, 6 and 2, and 7 and 1.
- Tell a quick story while setting the table, such as 'We need 10 cups and have 6 out,' and ask your child how many more to get.
- Toss a soft ball back and forth and say a fact within 5 with each catch, such as '2 and 3 is 5' or '4 take away 1 is 3.'
Where kids can get stuck
- Thinking 8 = 5 + 3 is backward because they expect the answer to come last.
- Counting the starting number as a step, so 6 seems to need 5 more to make 10 instead of 4.
- Knowing 4 + 1 but not 1 + 4, treating them as two different facts to learn.
Practice makes perfect
Bobby's Math Club has practice problems that adapt to your child’s level, each with a detailed explanation and an easy-to-follow video, so your child can build confidence in these skills one step at a time.
Words your child will hear
- compose
- To put smaller parts or shapes together to make something new.
- decompose
- To break a number or shape into smaller parts.
- part
- One of the smaller amounts a number can be broken into.
- whole
- The full amount that the parts make together.
- equation
- A math sentence with an equal sign, like 3 + 2 = 5.
- make ten
- Finding the number that goes with another to make 10, like 7 and 3.
- fact
- A small adding or subtracting problem kids learn to just know, like 2 + 2 = 4.
Ready to build your child’s confidence with making and breaking numbers?
In Bobby's Math Club, your child practices these skills 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.
Join the club
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.
Which math standards does Eureka Math² Kindergarten Module 4 cover?
Eureka Math² Kindergarten Module 4 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
For teachers: Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence. Learn how Bobby's Math Club can help your students grow.