What students learn in AC9M2N04
This unit helps students build a clear, usable understanding of Add and subtract one- and two-digit numbers, representing problems using.... The goal is not to memorise one answer pattern. Students should be able to explain the idea, recognise it in a new example and apply it in a short practice or worksheet task.
- Start with the main idea: add and subtract one- and two-digit numbers, representing problems using number sentences, and solve using part-part-whole reasoning and a variety of calculation strategies.
- Use concrete examples, pictures, oral explanation and short written responses before moving to independent practice.
- using the associative property of addition to assist with mental calculation by partitioning, rearranging and regrouping numbers using number knowledge, near doubles and bridging to 10 strategies; for example, calculating 7 + 8 using 7 + (7 + 1) = (7 + 7) + 1 , the associative property and near doubles; calculating 7 + 8 using the associative property and bridging to 10 , 7 + (3 + 5) = (7 + 3) + 5 using strategies such as doubles, near doubles, part-part-whole knowledge to 10, bridging tens and partitioning to mentally solve problems involving two-digit numbers; for example, calculating 56 + 37 by thinking 5 tens and 3 tens is 8 tens, 6 + 7 = 6 + 4 + 3 is one 10 and 3, and so the result is 9 tens and 3, 93
- Finish with mixed questions so students must choose the correct strategy rather than copy the last example.
Curriculum coverage and elaborations
The content description and elaborations below show the curriculum ideas taught in this unit. Items marked as teaching context support lesson planning but may not appear in the initial eight-question activity.
- Content description: add and subtract one- and two-digit numbers, representing problems using number sentences, and solve using part-part-whole reasoning and a variety of calculation strategies
- E1: using the associative property of addition to assist with mental calculation by partitioning, rearranging and regrouping numbers using number knowledge, near doubles and bridging to 10 strategies; for example, calculating 7 + 8 using 7 + (7 + 1) = (7 + 7) + 1 , the associative property and near doubles; calculating 7 + 8 using the associative property and bridging to 10 , 7 + (3 + 5) = (7 + 3) + 5
- E2: using strategies such as doubles, near doubles, part-part-whole knowledge to 10, bridging tens and partitioning to mentally solve problems involving two-digit numbers; for example, calculating 56 + 37 by thinking 5 tens and 3 tens is 8 tens, 6 + 7 = 6 + 4 + 3 is one 10 and 3, and so the result is 9 tens and 3, 93
- E3: representing addition and subtraction problems using a bar model and writing a number sentence, explaining how each number in the sentence is connected to the situation
- E4: using mental strategies and informal written jottings to help keep track of the numbers when solving addition and subtraction problems involving two-digit numbers and recognising that zero added to a number leaves the number unchanged; for example, in calculating 34 + 20 = 54, 3 tens add 2 tens is 5 tens which is 50, and 4 ones add zero ones is 4 ones which is 4, so the result is 50 + 4 = 54
- E5: using a physical or mental number line or hundreds chart to solve addition or subtraction problems, by moving along or up and down in tens and ones; for example, “I was given a \$100 gift card for my birthday and spent \$38 on a pair of shoes and \$15 on a t-shirt. How much money do I have left on the card?”
- E6: using First Nations Australians’ stories and dances to understand the balance and connection between addition and subtraction, representing relationships as number sentences (teaching context)
How to use this unit
Read the topic guide, use the teacher slide for instruction, then complete the Worksheet, Practice and Test. These three activities use the same eight-question unit bank.
Teacher resource
AC9M2N04 teacher slide
Use this one-page PDF to introduce the key idea, vocabulary and teaching sequence before students begin the activities.
Open teacher slide (PDF)Common mistakes to watch for
- Rushing to a rule before checking the concrete model, drawing or number sentence.
- Using the correct answer once but not being able to explain why it works.
- Mixing up similar vocabulary such as more/less, before/after, longer/shorter or equal groups/sharing.
International curriculum mapping
This table gives closest-topic mapping for search and planning. The Australian Curriculum code is exact; overseas entries are broad equivalents because each jurisdiction structures outcomes differently.
| Region | Curriculum | Closest mapping |
|---|---|---|
| Australia | Australian Curriculum v9.0 | AC9M2N04 — add and subtract one- and two-digit numbers, representing problems using number sentences, and solve using part-part-whole reasoning and a variety of calculation strategies |
| Victoria | Victorian Curriculum F-10 | Year 2 Maths: closest match in Number. Use this page as a VIC-aligned practice and worksheet reference. |
| NSW | NSW Curriculum | Stage 1 Maths: closest content focus for Add and subtract one- and two-digit numbers, representing problems using... and related outcomes. |
| United States | Common Core / NGSS | Grade 2 Common Core Mathematics/ELA closest topic match for Add and subtract one- and two-digit numbers, representing problems using.... |
| England / UK | National Curriculum | Key Stage 1 / Year 2: closest programme-of-study match for Add and subtract one- and two-digit numbers, representing problems using.... |
| Canada | Provincial and territory curricula | Grade 2 closest topic match. Canada varies by province, so use this as a broad Ontario/BC-style learning outcome reference. |
| New Zealand | New Zealand Curriculum | Level 1 Maths: closest achievement-objective topic for Add and subtract one- and two-digit numbers, representing problems using.... |
| India | NCERT / CBSE | Class 2 closest NCERT/CBSE topic match for Add and subtract one- and two-digit numbers, representing problems using.... |