Free printable practice
Decompse Numbers Under 20 Practice Activities
Printable early maths activities that help Nursery, LKG and UKG children split numbers under 20 into smaller parts for addition.
Practice that builds confidence
What children learn
These worksheets help Nursery, LKG and UKG children practise decomposing numbers under 20, which means breaking one number into two smaller parts. Children see that 8 can be 5 and 3, 10 and 0, or 4 and 4, building an early understanding of addition.
The printable activities use simple visuals such as dots, counters, boxes, ten frames, and number bonds. Children complete missing parts, match part-whole pictures, colour groups, and write simple addition pairs for numbers from 1 to 19.
Decomposing numbers teaches children that a number can be made in more than one way. Before formal sums become quick, young learners need to handle, see, and say the parts: “6 is 2 and 4” or “13 is 10 and 3.” This supports addition, mental maths, and later subtraction because children understand the relationship between the whole and its parts.
Progression in these practice sheets
The activities begin with small numbers shown through pictures, where children count two visible groups and find the total. They then move to part-whole models, number bonds, and missing-part tasks such as 9 = 6 + __. For numbers above 10, children practise noticing 10 and some more, such as 14 as 10 and 4. This keeps the work suitable for early years while gently preparing UKG children for written addition.
A simple parent routine
Use objects already at home: buttons, rajma, crayons, or building blocks. Give your child 7 objects and ask, “Can you split them into two groups?” After each split, say the full sentence together: “7 is 3 and 4.” Try a few different splits, then let your child complete one worksheet row. Keep the focus on talking about the parts, not racing through answers.
Classroom and centre use
Teachers can use these pages for small-group maths practice, morning work, revision after hands-on counting, or independent centres. Pair the worksheet with beads or counters so children can model the number before writing. For mixed readiness levels, some children can colour the groups first, while others can write several number pairs for the same whole.
Common errors to watch for
Young learners may count the whole again instead of counting each part, forget that 0 can be one part, or write numbers in the wrong box of a part-whole model. Some may think there is only one correct split. Encourage them to check by joining the parts and counting the whole again.
Free printable PDF download
Use this decompose numbers under 20 worksheet page to preview the activity, print it, or download it as a PDF for quick practice. It works well for homework, homeschool lessons, tutoring, morning work, revision, and classroom centers.
Answers and answer key support
After the child completes the worksheet independently, parents and teachers can use the answer support or answer key information to check the work, review mistakes, and choose the next practice step.
Why iBloom worksheets help
The pages use clear layouts, early-years vocabulary, and repeated visual patterns so children can understand the task quickly. A child-friendly strategy is: “Build it, split it, say it, write it.” This connects concrete objects, pictures, spoken maths, and written addition in one steady routine.
Helpful answers
Frequently asked questions
What does decomposing numbers under 20 mean for young children?
It means breaking one whole number into smaller parts, such as 12 as 10 and 2 or 7 as 4 and 3. This helps children understand how addition combinations work.
Are these worksheets suitable for Nursery children?
Yes, Nursery children can use the picture-based and counting-object activities with adult support. LKG and UKG children can move towards writing number pairs and filling missing parts.
Should children memorise all number bonds under 20?
At this stage, understanding is more important than memorising. Children should first build and split numbers with objects, then gradually recognise common pairs.
How can I explain 14 as 10 and 4 at home?
Ask your child to make a group of 10 objects and then place 4 more beside it. Say, “14 is 10 and 4,” then count all the objects to confirm the whole.
What should I do if my child always gives the same split?
Show the same number with counters and move one counter from one group to the other. For example, 8 can change from 5 and 3 to 4 and 4, while the whole stays 8.
Is this decompose numbers under 20 worksheet free?
Yes. You can preview it for free and use the printable worksheet for home or classroom practice.
Can I download this decompose numbers under 20 worksheet as a PDF?
Yes. Use the worksheet download option to save a printable PDF, or print the worksheet directly from the page.
Does this decompose numbers under 20 worksheet include answers or an answer key?
When the activity has fixed answers, iBloom includes answer support so parents and teachers can check the completed worksheet.