Addition — South Australian Year 3 Maths
Mental strategies first, then written addition of two- and three-digit numbers with and without regrouping, using the jump and split strategies. Five subtopics and 100 questions, aligned to AC9M3A02 and AC9M3N03.
Addition in South Australian Year 3
Addition is about joining amounts to find a total. In this topic Year 3 students move from quick mental strategies to written methods for two- and three-digit numbers, learning when and how to regroup a ten or a hundred.
The five subtopics below cover mental strategies for addition, adding two-digit numbers without and then with regrouping, adding three-digit numbers, and the jump and split strategies. Addition is one of the 18 topics in South Australian Year 3 Maths and draws on the Number and Algebra strands. It covers Australian Curriculum v9 codes AC9M3A02 and AC9M3N03. The same strategies are used in reverse in Subtraction, and they support the word problems in Addition and Subtraction Problems and in Money.
Subtopics
Addition: common questions
What does regrouping (carrying) mean?
When the ones add to 10 or more, 10 ones are swapped for 1 ten and written in the tens column. In \(46 + 28\), the ones make \(6 + 8 = 14\): write 4 and carry 1 ten. The tens then make \(4 + 2 + 1 = 7\), so the total is 74.
Which mental strategy should my child use?
It depends on the numbers. Split into tens and ones for \(42 + 16\), jump along a number line for \(67 + 25\), and for a number near a ten, add the ten and adjust: \(53 + 29 = 53 + 30 - 1 = 82\). Ask your child to explain why they chose a strategy.
What are common mistakes in written addition?
Lining up digits from the left instead of the right, forgetting a carried ten or hundred, and writing a two-digit total in one column. A quick estimate catches many slips: \(387 + 245\) is about \(400 + 200 = 600\), so an answer of 532, where the carried hundred was missed, needs checking. The real total is 632.
How can we practise addition at home?
Add prices in a catalogue or at the shops, keep score in card and board games, and add up distances on a car trip. Ask your child to work out a sum in their head and then check it with a written method, or the other way round.
Which curriculum codes cover Addition in South Australian Year 3?
The subtopics come under Australian Curriculum v9 codes AC9M3A02 (mental strategies built on known addition and subtraction facts) and AC9M3N03 (adding and subtracting by splitting and regrouping numbers by place value).