Understand the idea.
Track money in and money out
An enterprise is an organised activity that provides something, such as a class card stall. Money received from sales is income. Materials and other expenses are costs. Subtract the costs from income to find what is left.
Before starting, list the costs and the number of items expected to sell. Money spent making an unsold item still counts as a cost. Use all sales only when the question says those sales happen.
Explain who is affected
Money left after costs can support a class goal or a community project. Plan how much is saved, spent or donated. These amounts together cannot exceed the money left; the same dollar cannot be used twice.
Compare plans using both the calculations and the stated effects. Suitable donated materials may reduce costs and reuse resources. Explain that benefit only when the materials are available and suitable; do not assume every cheaper plan meets the same needs.
See the method in action.
Find money left
A class sells 12 cards for 3 dollars each. Supplies cost 14 dollars. All cards sell. How much is left after costs?
Worked solution
- 1
Find income from the card sales.
All 12 cards sell at 3 dollars each.
- 2
Pay the supply costs.
The supply cost must be allowed for before deciding what can be kept or donated.
- 3
Check the money is accounted for.
The 14 dollars spent and 22 dollars left use the full income.
22 dollars.
Compare two supply plans
Both plans sell 10 items for 4 dollars each. Plan A uses new supplies costing 25 dollars. Plan B uses suitable donated supplies plus extras costing 15 dollars. Compare the money left.
Worked solution
- 1
Find the income shared by both plans.
Both plans sell the same number of items for the same price.
- 2
Subtract Plan A costs.
Plan A spends 25 dollars on new supplies.
- 3
Subtract Plan B costs.
Plan B pays only 15 dollars for extras because the suitable donated supplies are free.
- 4
Compare the amounts left.
Plan B leaves 10 dollars more under the stated supply conditions.
A leaves 15 dollars; B leaves 25 dollars.
Try it yourself.
Check your understanding
A stall collects 50 dollars and has 18 dollars of costs. How much remains?
Show answer & reasoning
32 dollars
Subtract the costs from the income: dollars. The check shows that the costs and remainder account for all the money collected.
Keep practising
6 worksheet questions · 11 marks
Read the questions online
- A class sells 8 bookmarks at 3 dollars each. Find the income.1 mark
- A stall collects 45 dollars and pays 17 dollars for supplies. Find the money left.1 mark
- Find the supply total from the table.2 marks
Supply Cost Paper 12 dollars Ribbon 7 dollars Labels 4 dollars - Ten bags sell for 5 dollars each. Materials cost 28 dollars. The class donates 15 dollars from the money left. How much can it save?3 marks
- Two plans each collect 60 dollars. A costs 35 dollars and B costs 29 dollars. Which leaves more money, and by how much?2 marks
- The class plans to sell 20 items at 2 dollars each, with costs of 25 dollars. Only 10 sell. Can it still pay the costs from sales? Explain.2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- A class sells 8 bookmarks at 3 dollars each. Find the income.1 mark
.
24 dollars - A stall collects 45 dollars and pays 17 dollars for supplies. Find the money left.1 mark
.
28 dollars - Find the supply total from the table.2 marks
Supply Cost Paper 12 dollars Ribbon 7 dollars Labels 4 dollars .
23 dollars - Ten bags sell for 5 dollars each. Materials cost 28 dollars. The class donates 15 dollars from the money left. How much can it save?3 marks
Income .
After costs: ; after donation: .
7 dollars - Two plans each collect 60 dollars. A costs 35 dollars and B costs 29 dollars. Which leaves more money, and by how much?2 marks
A leaves 25; B leaves 31.
.
B leaves 6 dollars more. - The class plans to sell 20 items at 2 dollars each, with costs of 25 dollars. Only 10 sell. Can it still pay the costs from sales? Explain.2 marks
.
. Planned sales are not guaranteed.
No; sales bring 20 dollars, so 5 dollars is still needed.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics 2026
Estimating transactions; multi-step models; responsible purchases; class enterprise and community effects.
Official curriculum source ↗