Decimals — South Australian Year 4 Maths
Tenths and hundredths on bars, grids and number lines, linking fractions with decimals, and comparing and ordering decimals. Four subtopics and 80 questions with worked solutions, aligned to AC9M4N01 and AC9M4N03.
Decimals in South Australian Year 4
This topic extends place value past the ones into tenths and hundredths. Students show decimals on bars, hundred grids and number lines, say what each digit is worth, connect decimals with fractions out of 10 and 100, and then compare and order decimals.
The four subtopics are Represent Tenths, Represent Hundredths, Connect Fractions and Decimals, and Compare and Order Decimals. Decimals is one of the 20 topics in South Australian Year 4 Maths and belongs to the Number strand. It comes under Australian Curriculum codes AC9M4N01 (tenths and hundredths) and AC9M4N03 (fractions and decimals); the ordering in the last subtopic is Year 5 work in the Australian Curriculum (AC9M5N01). This work leads on to calculating with decimals, and to money and measurement.
Subtopics
Decimals: common questions
What is a tenth, and how is it written?
A tenth is one of ten equal parts of a whole. It can be written as the fraction \(\frac{1}{10}\) or the decimal \(0.1\). The first digit after the decimal point counts tenths, so \(0.4\) is four tenths and \(1.4\) is one whole and four tenths.
What does each digit in a decimal mean?
Each place is worth one tenth of the place to its left. In \(4.27\) the \(4\) is 4 ones, the \(2\) is 2 tenths and the \(7\) is 7 hundredths, so \(4.27 = 4 + 0.2 + 0.07\).
How do fractions and decimals connect?
The denominator tells you the place. A fraction out of \(10\) uses one decimal place and a fraction out of \(100\) uses two, so \(\frac{81}{100} = 0.81\). The same amount can have more than one name: \(\frac{20}{100} = \frac{2}{10} = 0.2\).
How do you compare decimals?
Line up the decimal points and compare the tenths first, then the hundredths. To compare \(0.4\) and \(0.38\), look at the tenths: \(4\) tenths is more than \(3\) tenths, so \(0.4\) is larger. A common mistake is thinking the decimal with more digits is always bigger.
Which curriculum codes cover Decimals in South Australian Year 4?
Australian Curriculum v9 code AC9M4N01 covers place value with tenths and hundredths, and AC9M4N03 covers linking fractions with decimals. Comparing decimals sits under AC9M4N01, while putting them in order is Year 5 work in the Australian Curriculum (AC9M5N01).