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Australia uses a point (.) as the decimal separator. For example, a number such as thirty thousand, two hundred and twelve point seven five would normally be written as 30 212.75 or 30,212.75

In Europe and some other countries around the world, however, the opposite is true. Points are used to separate large numbers, and commas are used for decimals. So, for example, the above number of 30,212.75 would be written as 30.212,75 – confusing, especially if you move or travel from one country to another where the system changes.

International Systems of Units (SI) – Trying to make things clear

To help overcome the confusion, the International Systems of Units (SI) recommends that a space should be used to separate groups of three digits, and both the comma and the point should be used to denote decimals. So, the above number under the SI system would be formally written as either 30 212.75 (which is how we would write it in Australia) or 30 212,75 (if we were living in Europe).

Here are examples of how you might see large numbers written.

Real-world uses of commas

From the Australian Bureau of Statistics (ABS) website

Source: https://www.abs.gov.au/statistics/people/population

Using the SI system

Following the SI system, this number would be written this way.

2C Tasks and questions

Thinking task

1 Using your favourite social media sites, take screenshots of five examples of different types of numbers.