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For example, we use negative numbers to measure temperature. Below we see a positive temperature on the left of +20°C and a negative number on the right of –20°C – which is 20° below zero.

Positive whole numbers and negative whole numbers can be shown on a number line, like the one shown below, with zero (0) in the centre.

You should remember that fractions and decimals are not integers.

Fractions

Whole numbers are exact amounts or marks on the number line, just like on a ruler or tape measure. The numbers that lie between the whole numbers, like 1 2 , 1 4 , 3 4 , are called fractions

Fractions are written with one number over another number like this: 3 4 3 4 or sometimes like this.

The bottom number of a fraction (called the denominator) tells you how many parts the whole has been broken up into, while the top number (the numerator) tells you how many of these parts you have.

Here are some examples.

Decimal numbers

Decimal numbers, like 0.3 and 43.6, are made up of a whole number part and a fraction part. The decimal point separates the whole number part on the left from the fraction part on the right.

Example: 43.6 (forty-three point six) is a decimal number made up of the whole number part (43) and the fraction part 0.6or

We will look at this in more detail later, as this relates to what we call place value.

Writing numbers: some conventions to follow

When we write decimal numbers and very big numbers, we need to keep the following things in mind.

Commas, full stops or spaces?

In Australia, we often use the comma (,) or a space to separate thousands, which makes large numbers easier to read.

So, for example, Australia’s population was 25 704 340 people as at 31 March 2021. Using commas, this is often written as 25,704,340