Understand the idea.
List the complete costs
A budget compares money available with the full cost of a plan. Multiply each unit price by the quantity needed, add each fixed fee once, then add the costs. Subtract the total from the available money to find what remains.
List every cost before deciding whether the plan is affordable: delivery, transport and booking charges can change the result. Separate required spending from optional purchases, and allow for unexpected costs where possible. The cheapest affordable option may still differ in quality or usefulness.
Compare whole plans
Compare complete plans for the same quantity or group size. A lower price per item can be offset by a fixed charge. Label the totals and the money remaining so a cheap advertised price is not mistaken for a complete cost.
Explain a purchase decision using the calculated totals and the stated priorities. If totals tie, price alone cannot choose between the options. If quality, reliability or another relevant cost is unknown, identify that gap instead of inventing information.
See the method in action.
A day-out budget
Maya has 100 AUD. Transport costs 18 AUD, food costs 32 AUD, and three tickets cost 12 AUD each. Find total spending and money left.
Worked solution
- 1
Calculate the ticket cost.
Three tickets each cost twelve dollars, so the unit price is counted three times.
- 2
Add all planned spending.
Transport, food and tickets are separate costs and each is included once.
- 3
Subtract from the available budget.
The remaining money is the starting amount less the complete cost.
86 AUD spent; 14 AUD left.
Include a fixed charge
Four meals cost 18 AUD each plus an 8 AUD delivery fee at A. At B, meals cost 20 AUD each with free delivery. Compare totals.
Worked solution
- 1
Calculate A's meal subtotal.
The required four meals each cost eighteen dollars at A.
- 2
Add A's fixed delivery charge.
The eight-dollar delivery fee applies once to the order.
- 3
Calculate B's complete total.
B charges twenty dollars per meal and adds no delivery fee.
- 4
Compare like-for-like totals.
Both four-meal orders cost the same, so price alone does not favour either option.
Both cost 80 AUD for four meals.
Try it yourself.
Check your understanding
A budget is 75 AUD and planned costs total 62 AUD. How much remains?
Show answer & reasoning
13 AUD
Subtract the complete planned spending from the money available: . A positive remainder means the stated plan fits the budget.
Keep practising
6 worksheet questions · 14 marks
Read the questions online
- A student has 60 AUD and spends 17 AUD on travel and 26 AUD on food. Find the amount left.2 marks
- Five entries cost 9 AUD each plus one 5 AUD booking fee. Find the total.2 marks
- A 40 AUD bag has 15% off. A student has 35 AUD. Can they afford it, and what remains?2 marks
- Plan A costs 12 AUD per person plus 10 AUD once. Plan B costs 14 AUD per person. Compare costs for six people.2 marks
- An event budget is 150 AUD. Room hire is 65 AUD, food is 48 AUD, and equipment is 22 AUD. Find the remaining amount. Should an optional 18 AUD decoration purchase be added without changing the budget?3 marks
- A school group can buy 20 durable cups for 24 AUD or 20 single-use cups for 10 AUD. They have a 25 AUD budget and expect repeated events. Give a justified choice, including one assumption.3 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- A student has 60 AUD and spends 17 AUD on travel and 26 AUD on food. Find the amount left.2 marks
Total cost: .
Remaining: .
17 AUD - Five entries cost 9 AUD each plus one 5 AUD booking fee. Find the total.2 marks
.
50 AUD - A 40 AUD bag has 15% off. A student has 35 AUD. Can they afford it, and what remains?2 marks
.
.
Yes; final price 34 AUD and 1 AUD remains. - Plan A costs 12 AUD per person plus 10 AUD once. Plan B costs 14 AUD per person. Compare costs for six people.2 marks
A: .
B: .
A: 82 AUD; B: 84 AUD; A is 2 AUD cheaper. - An event budget is 150 AUD. Room hire is 65 AUD, food is 48 AUD, and equipment is 22 AUD. Find the remaining amount. Should an optional 18 AUD decoration purchase be added without changing the budget?3 marks
Total: .
Remaining: .
Adding 18 gives total 153 AUD.
15 AUD remains; no, the extra purchase would exceed the budget by 3 AUD. - A school group can buy 20 durable cups for 24 AUD or 20 single-use cups for 10 AUD. They have a 25 AUD budget and expect repeated events. Give a justified choice, including one assumption.3 marks
Both initial purchases fit the budget.
Durable cups leave AUD; single-use cups leave 15 AUD.
The durable option may reduce repeated purchases, assuming safe reuse and cleaning; price alone does not decide.
Either justified decision is accepted; durable cups fit the budget and may be preferable if reused enough and cleaning is available.
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum
Percentage increase/decrease; finding an original amount; discounts and mark-ups; percentage comparisons; budgets and purchase decisions; modelling and checking financial problems with digital tools. Simple interest can be offered here as a school-dependent application and developed in Year 9.
Official curriculum source ↗