The idea, step by step
Track money in and money out
An enterprise is an organised activity that makes or provides something. A class might sell handmade cards to raise money. Money collected is income. Supplies and other expenses are costs. Money left after paying the costs is not the same as income.
Before starting, list quantities, prices and costs. Work out whether the plan can pay its costs and meet its goal. Do not assume every item will sell unless the question says it does. A real plan should also consider unsold items.
Explain who is affected
A financial decision can affect more than the buyer. The class may keep money for supplies, give some to a community project, or choose materials that can be reused. Use the actual cost and quantity information to explain a consequence.
Different goals can lead to different choices. A plan may raise less money but use fewer new materials. Explain the trade-off instead of calling one choice always right. Check that money spent, saved and donated does not exceed the money available.
A common trap
We collected 40 dollars, so we can donate all 40 and still pay our costs.
Instead: Pay or allow for costs first. Income minus costs is the amount available to save or donate.
See the thinking
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?
- Income: 12 × 3 = 36 dollars.
- Subtract supplies: 36 − 14 = 22 dollars.
- The class can use only 22 dollars for saving or donation, not the full 36.
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.
- Both plans collect 10 × 4 = 40 dollars.
- A leaves 40 − 25 = 15 dollars.
- B leaves 40 − 15 = 25 dollars, which is 10 dollars more. The comparison assumes the donated supplies are suitable and free.
Check your understanding
A stall collects 50 dollars and has 18 dollars of costs. How much remains?
Show answer
32 dollars
50 − 18 = 32 dollars; costs plus money left equals income.
Your turn
6 questions · 11 marks · Work at your own pace.
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
8 × 3 = 24.
24 dollars - A stall collects 45 dollars and pays 17 dollars for supplies. Find the money left.1 mark
45 − 17 = 28.
28 dollars - Find the supply total from the table.2 marks
Supply Cost Paper 12 dollars Ribbon 7 dollars Labels 4 dollars Paper 12 + ribbon 7 + labels 4 = 23.
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 10 × 5 = 50.
After costs: 50 − 28 = 22; after donation: 22 − 15 = 7.
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.
31 − 25 = 6.
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
10 × 2 = 20.
25 − 20 = 5. 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 ↗