Australian Currency & Money Math: ACARA Primary Guide
Australia was the first country in the world to introduce full polymer banknote technology. Practical financial mathematics for primary school.
Australia converted to decimal currency on 14 February 1966, replacing pounds, shillings, and pence with dollars and cents (100 cents = $1 AUD).
Under the Australian Curriculum (ACARA ACMNA059 and ACMNA080), primary students learn to count collections of mixed coins and notes, calculate total purchase prices, and work out change using counting-on strategies.
Why is the $2 Coin Smaller than the $1 Coin?
A frequent point of curiosity for young Australian learners is that the two-dollar coin has a smaller diameter (20.5 mm) than the one-dollar coin (25.0 mm).
The $2 coin was introduced in 1988 to replace the green paper $2 note. To help visually impaired citizens distinguish between coins by touch, the Reserve Bank designed the $2 coin with a significantly thicker edge (3.2 mm) and interrupted milled reeding, whereas the $1 coin is thinner.
Cash Transactions & 5-Cent Rounding
Since 1c and 2c copper coins were removed from circulation in 1992, cash transactions in Australia are rounded to the nearest five cents (electronic debit card transactions are never rounded):
• Total ending in 1c or 2c ➔ Round DOWN to 0c (e.g. $4.82 becomes $4.80).
• Total ending in 3c or 4c ➔ Round UP to 5c (e.g. $4.83 becomes $4.85).
• Total ending in 6c or 7c ➔ Round DOWN to 5c (e.g. $4.87 becomes $4.85).
• Total ending in 8c or 9c ➔ Round UP to 10c (e.g. $4.88 becomes $4.90).
✨ Key Takeaways
- 100 cents equal 1 Australian Dollar ($1.00 AUD).
- Silver coins are 5c, 10c, 20c, and 50c (12-sided dodecagon); gold coins are $1 and $2.
- The $2 coin is smaller in diameter than the $1 coin but substantially thicker with milled grooving.
- Cash totals are rounded to the nearest 5 cents using standard Swedish rounding rules.
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