💵 Money Calculations
Let's add and subtract Australian money amounts, and learn how to work out change at the shops!
✏️ Writing Money Amounts
We write dollars and cents using a decimal point. The dollars go before the point, and cents go after — always two digits.
$3.50
Three dollars and fifty cents
$0.75
Seventy-five cents
$12.05
Twelve dollars and five cents
Note: Always write two digits after the decimal point: $4.50 not $4.5, $0.05 not $0.5
➕ Adding Money
Add money amounts the same way as adding decimals — line up the decimal points!
A sandwich costs $4.50 and a drink costs $2.75. Total cost?
- Cents: 50 + 75 = 125 cents → write 25 cents, carry $1
- Dollars: $4 + $2 + $1 (carry) = $7
Total: $7.25 ✅
🔄 Making Change
Change is the money you get back when you pay more than the cost. Calculate change by subtracting the cost from the amount paid.
A toy costs $6.80. You pay with $10.00. How much change do you get?
Change: $3.20 ✅
Counting-on method: Start from $6.80 → $7.00 (20c) → $10.00 ($3.00) → total change = $3.20
Worked Examples
Example 1: Add three prices
Book: $5.95, Pencil case: $3.50, Eraser: $1.25. Total?
$5.95 + $3.50 = $9.45, then $9.45 + $1.25 = $10.70
Total: $10.70 ✅
Example 2: Change from $20
Lunch costs $13.40. Paid with $20. Change?
$20.00 − $13.40 = $6.60
Change: $6.60 ✅
Example 3: Can you afford it?
You have $8.00. A book costs $5.50 and stickers cost $3.00. Can you buy both?
$5.50 + $3.00 = $8.50. You only have $8.00.
No — $8.50 > $8.00. You are 50c short. ✅
Key Vocabulary
The dot separating dollars from cents, e.g. $4.50.
Money given back after paying more than the price.
The sum of all prices combined.
Adding up from the price to the amount paid to find change.
Knowledge Check
Question 1: A pie costs $3.50 and a juice costs $2.00. What is the total?
Question 2: A lolly bag costs $1.80. You pay with $5.00. What change do you receive?
Question 3: How do we write "six dollars and five cents"?
Question 4: Sam buys a hat for $8.75 and socks for $4.25. What is the total?
Question 5: Mia pays $50.00 for items totalling $37.60. What is her change?
Pax Says:
"Next time you are at the shops, try to add up the prices before you get to the counter — and see if you can guess the change you will get!"
Key Concepts Summary
- ✓ Write amounts with two digits after the decimal point: $4.50, $0.05.
- ✓ Add money by lining up decimal points and adding as usual.
- ✓ Change = amount paid − total cost.
- ✓ Count on from the cost to the amount paid to find change.