Budgeting and financial assumptions | Year 9

01 / LEARN

The idea, step by step

Account for the whole plan

A budget records expected income, expected costs and any amount to save or reserve. Add every cost once, subtract the total from income, and interpret the balance. A positive balance is money left; a negative balance is a shortfall.

For a school stall, separate costs that do not change with sales from costs per item. State any assumption about the number sold. Money expected from unsold items is not yet income.

Check an uncertain assumption

A budget is a model, so its inputs can be wrong. Recalculate for a lower income, higher cost or fewer sales to see whether the plan still works. A contingency amount can make the plan more realistic, but it must be included in the totals.

Use clear tables and consistent units. A balanced budget does not by itself prove a choice is best: non-financial needs, risk and the purpose of the plan can matter. Here the task is to justify the calculations under the supplied assumptions.

A common trap

Count money left before including a reserve or per-item expense.

Instead: List every planned cost and check whether it is fixed, per item or a reserve.

02 / WORKED EXAMPLES

See the thinking

Example 1

Worked example

A class has 240 dollars. Transport costs 135 dollars, materials 58 dollars and a reserve 20 dollars. Find the balance.

Total planned use $= 135 + 58 + 20 = 213$ dollars.
Balance $= 240 - 213 = 27$ dollars.
The reserve has already been included, not forgotten.

AUD 27.00 remains

Example 2

Worked example

A stall sells 30 items at 6 dollars each. Fixed costs are 50 dollars and each item costs 2 dollars to make. Find the surplus.

Income $= 30 \times 6 = 180$ dollars.
Costs $= 50 + 30 \times 2 = 110$ dollars.
Surplus $= 180 - 110 = 70$ dollars.

AUD 70.00

Check your understanding

Income is 90 dollars and costs are 105 dollars. What is the balance?

Show answer

AUD 15.00 shortfall

$90 - 105 = - 15$ .

03 / WORKSHEET

Your turn

6 questions · 15 marks · Work at your own pace.

Worksheet PDF Worked solutions

Read the questions online

A budget has 300 dollars income and costs of 125, 84 and 36 dollars. Find the balance.
2 marks
A budget has 300 dollars income, costs of 125, 84 and 36 dollars, and a 20-dollar reserve. Find the remaining available balance.
2 marks
A stall sells 20 items at 5 dollars. Costs are 30 dollars plus 2 dollars per item. Find its surplus.
3 marks
A stall sells and makes 15 items at 5 dollars each. Costs are 30 dollars fixed plus 2 dollars per item. Find the surplus.
3 marks
A 160-dollar transport estimate rises by 10%. How much extra must the budget allow?
2 marks
A plan balances only if every one of 40 tickets sells. Give a useful numerical stress test.
3 marks

Read the worked solutions

Equivalent correct methods earn the corresponding marks. Include units where asked.

A budget has 300 dollars income and costs of 125, 84 and 36 dollars. Find the balance.
2 marks
Costs $= 125 + 84 + 36 = 245$ .
$300 - 245 = 55$ .
AUD 55.00 remains
A budget has 300 dollars income, costs of 125, 84 and 36 dollars, and a 20-dollar reserve. Find the remaining available balance.
2 marks
$55 - 20 = 35$ .
AUD 35.00
A stall sells 20 items at 5 dollars. Costs are 30 dollars plus 2 dollars per item. Find its surplus.
3 marks
Income $= 100$ ; costs $= 30 + 40 = 70$ .
$100 - 70 = 30$ .
AUD 30.00
A stall sells and makes 15 items at 5 dollars each. Costs are 30 dollars fixed plus 2 dollars per item. Find the surplus.
3 marks
Income $= 75$ ; costs $= 30 + 30 = 60$ .
Surplus $= 15$ .
AUD 15.00
A 160-dollar transport estimate rises by 10%. How much extra must the budget allow?
2 marks
$0.10 \times 160 = 16$ .
AUD 16.00
A plan balances only if every one of 40 tickets sells. Give a useful numerical stress test.
3 marks
Keep all fixed costs unchanged.
Use $30 p$ rather than $40 p$ for ticket price $p$ , then check for a shortfall.
Recalculate income and balance for fewer sales, for example 30 tickets.

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Curriculum reference & lesson scope

Australian Curriculum v9 / SA Curriculum Mathematics

Year 9 financial modelling within AC9M9A05 and AC9M9M05; supplied hypothetical rates and costs, not financial advice.

Official curriculum source ↗

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