The idea, step by step
Money available sets a limit
A budget is a plan for the money you can use. If you have 8 dollars, a purchase costing 8 dollars or less fits that budget. A 9-dollar purchase does not. Add all the planned costs before deciding.
| Item | Price in dollars |
|---|---|
| Small notebook | 3 |
| Pencil set | 4 |
| Paint box | 9 |
Save towards a goal
Saving means keeping money for later instead of spending it now. If a book costs 12 dollars and you already have 7 dollars, you need 5 more. When you choose to spend some savings, check how that changes the amount still needed.
A common trap
Checking each price separately but not checking their combined cost.
Instead: Two items can each cost less than the budget while their total costs too much.
See the thinking
Check a budget
Leo has 8 dollars. He wants a 3-dollar notebook and a 4-dollar pencil set. Can he buy both? What will remain?
- Add the costs: 3 + 4 = 7 dollars.
- 7 is no more than 8. The remaining money is 8 − 7 = 1 dollar.
Plan saving
A craft kit costs 14 dollars. Isha has saved 8 dollars. She can save 2 dollars each week. How many more weeks will she need?
- She needs 14 − 8 = 6 more dollars.
- Count weekly additions: 2, 4, 6.
Check your understanding
You have 9 dollars and want a 12-dollar book. How much more must you save?
Show answer
3 dollars.
12 − 9 = 3.
Your turn
6 questions · Work at your own pace.
Read the questions online
- You have 6 dollars. Does a 5-dollar purchase fit your budget?
- You have 10 dollars. Can you buy items costing 6 dollars and 5 dollars together?
- A toy costs 15 dollars. You have 9 dollars. How much more must you save?
- You have saved 4 dollars. You save another 3 dollars. How much do you have?
- You need 8 more dollars and save 2 dollars each week. How many weeks are needed?
- You have 10 dollars for a 10-dollar book. If you buy a 2-dollar sticker first, can you still buy the book now? Explain.
Read the worked solutions
- You have 6 dollars. Does a 5-dollar purchase fit your budget?
6 − 5 = 1.
Yes; 1 dollar remains. - You have 10 dollars. Can you buy items costing 6 dollars and 5 dollars together?
6 + 5 = 11, which is greater than 10.
No. You need 1 dollar more. - A toy costs 15 dollars. You have 9 dollars. How much more must you save?
15 − 9 = 6.
6 dollars. - You have saved 4 dollars. You save another 3 dollars. How much do you have?
4 + 3 = 7.
7 dollars. - You need 8 more dollars and save 2 dollars each week. How many weeks are needed?
Count 2, 4, 6, 8.
4 weeks. - You have 10 dollars for a 10-dollar book. If you buy a 2-dollar sticker first, can you still buy the book now? Explain.
Spending changes the money available for the goal.
No. You would have 8 dollars, so you would need 2 more.
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 ↗