AC9M2N02
Official content description
partition, rearrange, regroup and rename two- and three-digit numbers using standard and non-standard groupings; recognise the role of a zero digit in place value notation
What AC9M2N02 actually looks like when you teach it
This is the descriptor that makes written subtraction possible two years later, so it's worth more time than it usually gets. Renaming 342 as 3 hundreds 4 tens 2 ones is the easy half; renaming it as 2 hundreds 14 tens 2 ones is the half that matters and the half that gets skipped. Do it with MAB, out loud, repeatedly, before any algorithm appears. The zero digit deserves its own attention too — in 406 the zero isn't nothing, it's a placeholder holding the hundreds apart from the ones, and children need to say that.
What the class will get wrong — and what to do about it
The error
Treating zero as "nothing there, so ignore it" — 406 read or written as 46, or the tens column left blank because there aren't any.
How to confront it
Build 406 and 46 side by side in MAB and ask which is bigger and why. Then ask what would happen to 406 if the zero were rubbed out. The zero earns its place when its absence visibly changes the number.
Ready to put on the board
We are learning to rename numbers in more than one way, and to explain what a zero digit is doing.
- I can rename a three-digit number in a non-standard way, like 14 tens and 2 ones.
- I can explain why the zero in 406 matters.
- I can regroup ten ones into a ten, and ten tens into a hundred.
Same number, different bundles
- Give each pair 235 in MAB, built the standard way. They record it: 2 hundreds, 3 tens, 5 ones.
- Challenge: build the same number using no hundreds. Let them work it out — they'll trade.
- Record the new build: 23 tens and 5 ones. Same number, different bundles.
- One more: build it with only 1 hundred. Record.
- Discuss: the number didn't change. What changed? This is exactly the move they'll need for subtraction with regrouping.
Free to use in your classroom. Written for AC9M2N02, not adapted from another year level.
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The Year 2 Maths planning scaffold
A one-page planning sheet with the official achievement standard, every content description grouped by strand, and space for your assessment and week-by-week sequence. Print it and plan on paper, or use it as the skeleton for a unit.
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What Year 2 Maths students should achieve
Coverage is judged against the achievement standard — not by ticking every content description. These are the official Year 2 Maths standard sentences this code builds towards:
- Students recall and demonstrate proficiency with addition and subtraction facts within 20 and multiplication facts for twos.
- Students locate and identify positions of features in two-dimensional representations and move position by following directions and pathways.
- Students identify and represent part-whole relationships of halves, quarters and eighths in measurement contexts.
- They use mathematical modelling to solve practical additive and multiplicative problems, including money transactions, representing the situation and choosing calculation strategies.
- They compare and classify shapes, describing features using formal spatial terms.
- They describe and continue patterns that increase and decrease additively by a constant amount and identify missing elements in the pattern.
The Number progression either side of AC9M2N02
A class can only meet this descriptor if they were taught the one before it. If yours hasn't, that's where the lesson starts — not here.
Taught before · Year 1
- AC9M1N01recognise, represent and order numbers to at least 120 using physical and virtual materials, numerals, number lines and charts
- AC9M1N02partition one- and two-digit numbers in different ways using physical and virtual materials, including partitioning two-digit numbers into tens and ones
- AC9M1N03quantify sets of objects, to at least 120, by partitioning collections into equal groups using number knowledge and skip counting
Builds towards · Year 3
- AC9M3N01recognise, represent and order natural numbers using naming and writing conventions for numerals beyond 10 000
- AC9M3N02recognise and represent unit fractions including 1/2, 1/3, 1/4, 1/5 and 1/10 and their multiples in different ways; combine fractions with the same denominator to complete the whole
- AC9M3N03add and subtract two- and three-digit numbers using place value to partition, rearrange and regroup numbers to assist in calculations without a calculator
Other Year 2 Number codes
- AC9M2N01recognise, represent and order numbers to at least 1000 using physical and virtual materials, numerals and number lines
- AC9M2N03recognise and describe one-half as one of 2 equal parts of a whole and connect halves, quarters and eighths through repeated halving
- AC9M2N04add 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
- AC9M2N05multiply and divide by one-digit numbers using repeated addition, equal grouping, arrays, and partitioning to support a variety of calculation strategies
- AC9M2N06use mathematical modelling to solve practical problems involving additive and multiplicative situations, including money transactions; represent situations and choose calculation strategies; interpret and communicate solutions in terms of the situation
Content description and achievement standard © Australian Curriculum, Assessment and Reporting Authority (ACARA), Australian Curriculum Version 9, used under CC BY 4.0. TeachKoala is not affiliated with or endorsed by ACARA.