Mathematics Standard • Year 11 • Module 3 • Lesson 10
Managing Money — Exam Practice
Apply the full Managing Money toolkit to realistic, multi-part Australian workplace and household scenarios.
Reference — 2024–25 ATO tax brackets
| Taxable income | Tax on this income |
|---|---|
| $0 – $18,200 | Nil |
| $18,201 – $45,000 | Nil + 19c for each $1 over $18,200 |
| $45,001 – $120,000 | $5,092 + 32.5c for each $1 over $45,000 |
| $120,001 – $180,000 | $29,467 + 37c for each $1 over $120,000 |
| $180,001 + | $51,667 + 45c for each $1 over $180,000 |
Medicare levy = 2% of taxable income. GST = 10% (×1.10, ÷1.10, ÷11).
Problem 1 — Hospitality worker chains net pay → budget
Mia works as a café manager. Her gross fortnightly pay is $2,380. Fortnightly deductions: PAYG tax $364; union $14; super (employee top-up) $68; private health insurance $42. Her monthly expenses are: rent $1,840; groceries $620; transport $220; phone $58 (GST-inclusive); annual insurance $720 (GST-inclusive).
Set up: What are we solving for?
(i) Calculate Mia's fortnightly net pay. 1 mark
(ii) Convert all her income and expenses to monthly figures. Calculate total monthly income and total monthly expenses. 3 marks
(iii) Calculate Mia's monthly surplus or deficit and state a clear conclusion. 2 marks
Stuck? Fortnightly net pay × 26 ÷ 12 = monthly net pay; annual insurance ÷ 12 = monthly.Problem 2 — Self-employed plumber: deductions → tax → debt
Daniel is a self-employed plumber. He earned $108,600 in gross fees and $640 in bank interest. His allowable deductions are: $1,860 work tools, $980 vehicle running costs, $420 union/trade fees, $260 donation to a registered DGR, plus $480 conventional clothes worn at client meetings (not allowable). His PAYG instalments totalled $24,400.
Set up: What are we solving for?
(i) Calculate the total allowable deductions and Daniel's taxable income. 2 marks
(ii) Calculate Daniel's income tax, Medicare levy and total tax liability. 3 marks
(iii) Determine whether Daniel receives a refund or owes a debt and state the dollar amount. 1 mark
Stuck? Conventional clothing is not allowable — exclude $480 before summing deductions.Problem 3 — Comparing internet plans for a household
The Walsh household uses 110 GB of internet per month. Two providers are quoted GST-inclusive:
Plan A: $89/month unlimited data.
Plan B: $42/month base + $0.45 per GB above 50 GB.
Set up: What are we solving for?
(i) Calculate Plan B's expected monthly cost based on 110 GB usage. 2 marks
(ii) Which plan is cheaper, and by how much per month and per year? 2 marks
(iii) Calculate the GST component of the chosen (cheaper) plan's monthly cost. 1 mark
Stuck on (iii)? Quoted prices are GST-inclusive — use ÷11.Problem 4 — Two pay-rise scenarios
Sienna's current taxable income is $76,400. PAYG withheld $15,920 per year. Her employer offers two options for a pay rise:
Option A: $5,400 salary increase, but PAYG withholding rises to $17,650.
Option B: $3,600 salary increase + an extra $1,800 in employer-paid super (super is NOT added to taxable income for this question), with PAYG withholding $16,820.
Set up: What are we solving for?
(i) Under Option A: calculate her new taxable income, total tax liability, and refund/debt. 2 marks
(ii) Under Option B: calculate her new taxable income, total tax liability, and refund/debt. 2 marks
(iii) Compare Sienna's after-tax cash income under each option (taxable income − total liability + any refund / − any debt). Which option leaves her better off this year, and by how much? 2 marks
Stuck on (iii)? After-tax cash = taxable income − total tax liability. The PAYG withholding determines the refund/debt but doesn't change after-tax cash, which depends on actual tax owed.Problem 5 — Quarterly bill audit
The Patel family receives a quarterly electricity bill. The provider's pre-GST rates are: supply $1.12/day for 91 days; first 800 kWh at 28.6c/kWh, remaining at 36.4c/kWh. The household used 1,120 kWh this quarter. The printed bill (GST-inclusive) shows $612.40.
Set up: What are we solving for?
(i) Calculate the correct pre-GST total. 2 marks
(ii) Calculate the correct GST-inclusive total. 1 mark
(iii) Compare with the printed $612.40 and state whether the bill is over- or under-charged, and by how much. Then state the GST component on the correct total. 2 marks
Stuck? Always sum supply + Tier 1 + Tier 2 first as pre-GST, then ×1.10 for inclusive, then ÷11 for the GST component if asked.How did this worksheet feel?
What I'll revisit before next class:
Problem 1 — Mia: net pay → monthly budget
Set up. Find fortnightly net pay first, then convert to monthly. Convert annual insurance to monthly. Compare income against expenses.
(i) Total fortnightly deductions = $364 + $14 + $68 + $42 = $488. Net pay = $2,380 − $488 = $1,892 per fortnight.
(ii) Monthly net pay = $1,892 × 26 ÷ 12 ≈ $4,099.33.
Monthly expenses = $1,840 + $620 + $220 + $58 + ($720 ÷ 12) = $1,840 + $620 + $220 + $58 + $60 = $2,798.00.
(iii) Surplus = $4,099.33 − $2,798.00 = $1,301.33 monthly surplus. Mia has a comfortable surplus of about $1,301 per month — well-positioned to save or pay down debt.
Problem 2 — Daniel: plumber's tax
Set up. Sort allowables, calculate taxable income, apply bracket + Medicare, reconcile.
(i) Allowable deductions = $1,860 + $980 + $420 + $260 = $3,520 ($480 conventional clothes excluded).
Gross income = $108,600 + $640 = $109,240. Taxable income = $109,240 − $3,520 = $105,720.
(ii) $105,720 in $45,001 – $120,000 bracket. Income tax = $5,092 + 0.325 × ($105,720 − $45,000) = $5,092 + 0.325 × $60,720 = $5,092 + $19,734 = $24,826.00. Medicare = $105,720 × 0.02 = $2,114.40. Total liability = $26,940.40.
(iii) PAYG $24,400 < $26,940.40 → tax debt of $2,540.40.
Problem 3 — Internet plans
Set up. Compute Plan B's variable cost for 110 GB; compare; then extract GST from the cheaper inclusive cost.
(i) Plan B = $42 + (110 − 50) × $0.45 = $42 + 60 × $0.45 = $42 + $27.00 = $69.00 per month.
(ii) Plan B is cheaper. Monthly saving = $89 − $69 = $20.00 per month. Annual saving = $20 × 12 = $240.00 per year.
(iii) GST component of Plan B = $69 ÷ 11 ≈ $6.27 per month.
Problem 4 — Sienna's pay rise
Set up. Calculate taxable income, total liability, and refund/debt for each option; then compare after-tax cash.
(i) Option A. New taxable income = $76,400 + $5,400 = $81,800. Income tax = $5,092 + 0.325 × ($81,800 − $45,000) = $5,092 + 0.325 × $36,800 = $5,092 + $11,960 = $17,052. Medicare = $81,800 × 0.02 = $1,636. Total liability = $18,688. PAYG $17,650 < $18,688 → tax debt of $1,038.
(ii) Option B. New taxable income = $76,400 + $3,600 = $80,000 (super not included). Income tax = $5,092 + 0.325 × ($80,000 − $45,000) = $5,092 + 0.325 × $35,000 = $5,092 + $11,375 = $16,467. Medicare = $80,000 × 0.02 = $1,600. Total liability = $18,067. PAYG $16,820 < $18,067 → tax debt of $1,247.
(iii) After-tax cash (Option A) = $81,800 − $18,688 = $63,112. After-tax cash (Option B) = $80,000 − $18,067 = $61,933. Option A leaves her $63,112 − $61,933 = $1,179 better off in cash this year (although Option B gives her $1,800 extra into super for retirement — a separate consideration not asked here).
Problem 5 — Bill audit
Set up. Calculate the correct bill from rates, compare with printed total, find the GST component.
(i) Supply = $1.12 × 91 = $101.92. Tier 1 = 800 × $0.286 = $228.80. Tier 2 = (1,120 − 800) × $0.364 = 320 × $0.364 = $116.48. Pre-GST = $101.92 + $228.80 + $116.48 = $447.20.
(ii) GST-inclusive = $447.20 × 1.10 = $491.92.
(iii) Printed $612.40 vs correct $491.92 → bill is over-charged by $120.48. GST component of correct total = $491.92 ÷ 11 ≈ $44.72. (Conclusion: the Patels should query the provider — they have been over-billed by $120.48.)