The idea, step by step
Join the costs
Buying two different things means paying both prices. A 3-dollar pencil and a 4-dollar ruler cost 7 dollars altogether. Write what the numbers count so you do not confuse the number of items with their prices.
Change is money returned
If the payment is more than the cost, the difference is returned as change. A 10-dollar payment for a 7-dollar purchase gives 3 dollars change. Check by joining the cost and the change: 7 + 3 = 10.
A common trap
Adding the payment and cost to find change.
Instead: The payment already includes the cost. Change is the money left after the cost is taken out.
See the thinking
Buy two items
A bookmark costs 2 dollars and a pen costs 5 dollars. How much do they cost together?
- Both prices must be paid.
- 2 + 5 = 7.
Find the change
A puzzle costs 8 dollars. Mia pays with a 10-dollar note. What change should she get?
- Count from the cost, 8 dollars, up to the payment, 10 dollars.
- The difference is 2 dollars; check 8 + 2 = 10.
Check your understanding
You buy a 4-dollar item and pay 5 dollars. What change do you get?
Show answer
1 dollar.
5 − 4 = 1.
Your turn
6 questions · Work at your own pace.
Read the questions online
- A card costs 3 dollars and a sticker sheet costs 2 dollars. Find the total cost.
- Two postcards cost 2 dollars each. Find their total cost.
- An item costs 6 dollars. You pay 10 dollars. Find the change.
- A bag costs 9 dollars. Can you pay exactly with four 2-dollar coins and one 1-dollar coin?
- A pen costs 3 dollars and a pad costs 5 dollars. You have 7 dollars. How much more is needed?
- A game costs 7 dollars. You pay 10 dollars and receive 2 dollars change. Is the change correct? Explain.
Read the worked solutions
- A card costs 3 dollars and a sticker sheet costs 2 dollars. Find the total cost.
3 + 2 = 5.
5 dollars. - Two postcards cost 2 dollars each. Find their total cost.
2 + 2 = 4.
4 dollars. - An item costs 6 dollars. You pay 10 dollars. Find the change.
10 − 6 = 4.
4 dollars. - A bag costs 9 dollars. Can you pay exactly with four 2-dollar coins and one 1-dollar coin?
2 + 2 + 2 + 2 + 1 = 9.
Yes. - A pen costs 3 dollars and a pad costs 5 dollars. You have 7 dollars. How much more is needed?
The total cost is 8 dollars; 8 − 7 = 1.
1 dollar. - A game costs 7 dollars. You pay 10 dollars and receive 2 dollars change. Is the change correct? Explain.
7 + 2 = 9, not 10. The correct check is 7 + 3 = 10.
No. It should be 3 dollars change.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Comparing prices; $1/$2 coins and notes; purchases; limited money and saving; needs/wants; consumer choices.
Official curriculum source ↗