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Mathematics / Year 3 / Number
Curriculum content descriptions
add and subtract two- and three-digit numbers using place value to partition, rearrange and regroup numbers to assist in calculations without a calculator (AC9M3N03)
Elaborations
- using partitioning and part-part-whole models and the inverse relationship between addition and subtraction to solve addition or subtraction problems, making informal written “jottings” to keep track of the numbers if necessary
- using physical or virtual grouped materials or diagrams to make proportional models of numbers to assist in calculations; for example, to calculate \(214 + 325\) representing \(214\) as \(2\) groups of \(100\), one group of \(10\) and \(4\) ones and \(325\) as \(3\) groups of \(100, 2\) groups of \(10\) and \(5\) ones resulting in \(5\) groups of \(100, 3\) groups of \(10\) and \(9\) ones which is \(539\)
- choosing between standard and non-standard place value partitions to assist with calculations; for example, to solve \(485 + 365\), thinking of \(365\) as \(350 + 15\), then adding the parts, \(485 + 15 = 500\), \(500 + 350 = 850\)
- solving subtraction problems efficiently by adding or subtracting a constant amount to both numbers to create an easier calculation; for example, \(534 \space– \space395\) adding \(5\) to both numbers to make \(539 \space – \space400 = 139\)
- justifying choices about partitioning and regrouping numbers in terms of their usefulness for particular calculations when solving problems
- applying knowledge of place value to assist in calculations when solving problems involving larger numbers; for example, calculating the total crowd numbers for an agricultural show that lasts a week
General capabilities
ScOT terms
Associativity, Written calculations, Subtraction, Place value, Addition