Whole Numbers and Place Value — South Australian Year 4 Maths
Odd and even numbers by pairing and the ones digit, then rounding to the nearest 10, 100 or 1000, with halfway numbers. Two subtopics and 40 questions with worked solutions, aligned to AC9M4N02 and AC9M4N07.
Whole Numbers and Place Value in South Australian Year 4
This topic works with the properties of whole numbers. It starts with odd and even numbers, told apart by pairing or by the ones digit, and moves on to rounding, which students then use to estimate and check calculations in the Addition, Subtraction and Money topics.
The two subtopics are Odd and Even Numbers, and Round Numbers to the Nearest 10, 100 or 1000. Whole Numbers and Place Value is one of the 20 topics in South Australian Year 4 Maths and belongs to the Number strand. It comes under Australian Curriculum codes AC9M4N02 (odd and even numbers) and AC9M4N07 (estimating and rounding). These skills lead on to factors, multiples and estimating with larger numbers in later years.
Subtopics
Whole Numbers and Place Value: common questions
How can you tell if a number is odd or even?
Look only at the ones digit. If the last digit is \(0, 2, 4, 6\) or \(8\) the number is even, and if it is \(1, 3, 5, 7\) or \(9\) the number is odd, however big it is, so \(3476\) is even. With counters, an even number makes pairs with none left over.
What happens when you add odd and even numbers?
Odd plus odd is even, as in \(7 + 9 = 16\). Even plus even is also even, and odd plus even is odd, as in \(6 + 11 = 17\). Children can check each rule with counters by pairing them up.
Which digit do you check when rounding to the nearest 10, 100 or 1000?
For the nearest ten check the ones digit, for the nearest hundred the tens digit and for the nearest thousand the hundreds digit. If it is \(5\) or more, round up; if it is \(4\) or less, round down. So \(3640\) is \(3600\) to the nearest hundred and \(4000\) to the nearest thousand.
What happens to a number that is exactly halfway?
A number exactly halfway always rounds up, so \(25\) becomes \(30\) and \(7500\) becomes \(8000\). Common mistakes are checking the wrong digit and changing a number that is already a multiple of ten: \(380\) stays \(380\) to the nearest ten. At home, round the prices on a receipt or the distances on road signs.
Which curriculum codes cover Whole Numbers and Place Value in South Australian Year 4?
Odd and even numbers come under Australian Curriculum v9 code AC9M4N02, and rounding comes under AC9M4N07, which is about using rounded numbers to estimate and to judge whether an answer, including a money calculation, makes sense.