AC9M1N04 • Year 1 Maths
Addition joins parts to make a whole. Subtraction can remove a part or find a missing part. Strategies help us work within 20.
Addition joins parts to make a whole. Subtraction can remove a part or find a missing part. Strategies help us work within 20.
Learning routine: Read → Model → Choose strategy → Calculate → Check
For subtraction, think about the missing part or count back carefully.
Do not use one strategy for every problem; choose the one that fits.
Explain your thinking: Say what each part of the model represents, then explain why the answer or conclusion follows.
Explain an addition or subtraction strategy using parts within 20.
Work out 8 + 5 without counting all thirteen objects from one.
Watch for this mistake: Do not use the whole five again after making ten. The two used and the three left must still total five.
Use ten to solve 9 + 4. Show how you split 4.
Nine needs one more.
Split 4 into 1 and 3: 9 + 1 + 3 = 13.
Find 14 - 6 by going back through ten.
First remove enough to reach ten.
14 - 4 = 10; two more must be removed, so 10 - 2 = 8.
These curriculum examples extend the central model into varied contexts. They are learning contexts, not extra definitions to memorise.
using drawings, physical and virtual materials and number combinations within 10 to add and subtract collections to 20
Try and explain: Draw 15 counters and cross out six. What remains, and which number sentence matches?
Nine remain. 15 − 6 = 9; the crossed-out counters show the amount taken away.
adding and subtracting numbers within 20, using a variety of representations and strategies such as counting on, counting back, partitioning and part-part-whole knowledge of numbers to 10; for example, using partitioning and combining 7+5=7+3+2=10+2=12
Try and explain: Use making ten to calculate 9 + 5. Explain how you split five.
Split five into one and four: 9 + 1 + 4 = 10 + 4 = 14.
developing and using strategies for one-digit addition and subtraction based on part-part-whole relationships for each of the numbers to 10 and subitising with physical and virtual materials; for example, 8 and 6 is the same as 8 and 2 and 4
Try and explain: You know 6 + 6 = 12. How does that help find 6 + 7?
Seven is one more than six, so the total is one more than 12: 13.
representing story problems involving addition and subtraction of numbers within 20 using a Think Board, recognising and using + and - symbols and the equal sign to represent the operations of addition and subtraction; showing and explaining the connections between any materials used using the language of plus and minus, and the numbers within the story problem
Try and explain: Ten birds sit on a fence. Four more arrive. Draw the story and write an equation that matches.
10 + 4 = 14. The drawing should join a group of ten and a group of four; fourteen is the whole.
creating and performing addition and subtraction stories told through First Nations Australians’ dances
Cultural safety: Use a community-approved source, name the specific Nation or community where the source does, and avoid presenting diverse First Nations knowledges as one generic tradition. Follow local cultural and intellectual property protocols before inviting community participation.
Use counters to show 9 + 6 and make ten first.
Model: 9 + 1 + 5
Solve 14 − 6 by asking 6 + ? = 14.
Model: 6 + 8 = 14
Explain which strategy you used and why.
Model: I used make ten because...
Key idea: Addition joins parts to make a whole. Subtraction can remove a part or find a missing part. Strategies help us work within 20.
Return to the concept model if an answer is uncertain. Use the model to explain, not just to guess.
AC9M1N04: add and subtract numbers within 20, using physical and virtual materials, part-part-whole knowledge to 10 and a variety of calculation strategies
Use the Practice Sheet for written or hands-on work, Practice for supported feedback, and Test when the student is ready to demonstrate independent mastery.
The SkillrHub lesson remains the primary learning resource. This optional video reinforces the explanation; you can complete the lesson and practice without watching.
Before you watch:
Scratch Garden — Use parts and a whole to support addition and subtraction within 20.
As you watch: Notice how the parts fit together to make the whole.
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Try it: Show 10 as 6 and 4. Say one addition fact and one subtraction fact that match your counters.
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Mapped skill: add and subtract numbers within 20, using physical and virtual materials, part-part-whole knowledge to 10 and a variety of calculation strategies
These references identify matching or closely related learning. Curriculum sequence, terminology and depth vary, so teachers should use the mapped skill and lesson difficulty to confirm suitability.
| Region | Curriculum framework | Closest level or code |
|---|---|---|
| Australia | Australian Curriculum v9.0 | AC9M1N04 · Year 1 |
| Victoria | Victorian Curriculum F–10 Version 2.0 — Mathematics | VC2M1N04 · Level 1 |
| New South Wales | NSW Mathematics K–10 Syllabus (2022) | MA1-CSQ-01 · Stage 1 |
| United States (USA) | Common Core State Standards for Mathematics | Grade 1 |
| Canada (Ontario) | Ontario Curriculum — Mathematics | Grade 1 |
| United Kingdom (England) | National Curriculum in England — Mathematics | Year 2, Key Stage 1 |
| India | NCERT / CBSE — Mathematics | Class 1 |
Australian Curriculum v9.0 is the canonical source for this SkillrHub lesson. Victoria and NSW entries name the closest published state codes or outcomes; international entries are planning references rather than claims of identical curricula.
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Topic reference: AC9M1N04 — Addition and Subtraction within 20
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