Mathematics Standard • Year 11 • Module 3 • Lesson 10
Managing Money — Exam Practice
Practise HSC Mathematics Standard 2-style writing on Managing Money — short answers and one structured extended response that chains tax, budgeting and GST.
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).
1. Short-answer questions
1.1 A worker has gross fortnightly pay of $2,140. Fortnightly deductions are PAYG tax $352, union $14, super top-up $76. Calculate the fortnightly net pay. 2 marks Band 3
1.2 Aisha earns $72,800 salary and $620 in bank interest. Her allowable deductions total $2,180. Her PAYG withheld was $14,650.
(a) Calculate Aisha's taxable income.
(b) Calculate her total tax liability (income tax + Medicare levy).
(c) State whether she has a refund or debt and the amount. 4 marks Band 3-4
1.3 A 91-day GST-inclusive electricity bill is $487.30. Pre-GST rates: supply $0.98/day; flat usage 27.4c/kWh.
(a) Calculate the pre-GST amount on the printed bill.
(b) Hence determine how many kWh the household used this quarter (to the nearest kWh). 4 marks Band 4
2. Extended response
2.1 Brendan is a software developer. For the 2024–25 financial year he reports the following:
Income: salary $94,400; bank interest $820; rental income from a granny flat $1,640.
Allowable deductions: union/professional fees $560; home-office equipment $1,140; registered DGR donation $300. (Also listed: $480 commute home-to-CBD office — NOT allowable.)
PAYG withheld by employer: $23,800 for the year.
Monthly expenses: rent $2,180; weekly groceries $290; quarterly electricity bill $568 (GST-inclusive); monthly phone $94 (GST-inclusive); annual insurance $1,680 (GST-inclusive).
(a) Calculate Brendan's taxable income (justify excluding the commute).
(b) Calculate his income tax, Medicare levy and total tax liability. State refund or debt.
(c) Convert all monthly expenses to a single monthly figure. Calculate his after-tax monthly cash income (divide annual after-tax income by 12), and find his monthly surplus or deficit. Also state the GST component of the electricity bill. 7 marks Band 5-6
Explicit marking criteria
Part (a) — 2 marks
• 1 mark — correctly identifies allowable deductions and excludes the $480 commute with a brief reason.
• 1 mark — correct taxable income (gross from three sources − allowable deductions).
Part (b) — 2 marks
• 1 mark — correct income tax + Medicare = total tax liability.
• 1 mark — correct refund or debt amount with conclusion sentence.
Part (c) — 3 marks
• 1 mark — correctly converts weekly/quarterly/annual expenses to monthly and totals them.
• 1 mark — correct monthly after-tax cash and monthly surplus/deficit.
• 1 mark — correct GST component of electricity using ÷11 on the GST-inclusive amount.
Your response:
Stuck on (c)? After-tax annual income = taxable income − total liability. Divide by 12 to get monthly cash. Compare with monthly expenses for surplus/deficit.How did this worksheet feel?
What I'll revisit before next class:
1.1 — Net pay (2 marks)
Sample response.
Total deductions = $352 + $14 + $76 = $442.
Net pay = $2,140 − $442 = $1,698.00 per fortnight.
Marking notes. 1 mark — correctly sums all three deductions. 1 mark — correct net pay with units.
1.2 — Aisha's tax (4 marks)
Sample response.
(a) Gross = $72,800 + $620 = $73,420. Taxable income = $73,420 − $2,180 = $71,240.
(b) Income tax = $5,092 + 0.325 × ($71,240 − $45,000) = $5,092 + $8,528 = $13,620. Medicare = $71,240 × 0.02 = $1,424.80. Total liability = $15,044.80.
(c) $14,650 < $15,044.80 → tax debt of $394.80.
Marking notes. (a) 1 mark — correct taxable income (gross with interest, minus deductions). (b) 1 mark — correct income tax. 1 mark — correct Medicare + total liability. (c) 1 mark — correct direction and conclusion sentence.
1.3 — Reverse-engineering kWh (4 marks)
Sample response.
(a) Pre-GST = $487.30 ÷ 1.10 = $443.00.
(b) Supply = $0.98 × 91 = $89.18. Usage cost = $443.00 − $89.18 = $353.82. kWh = $353.82 ÷ $0.274 = 1291.31... ≈ 1,291 kWh (to nearest kWh).
Marking notes. (a) 1 mark — uses ÷1.10 (not ÷11). 1 mark — correct pre-GST amount. (b) 1 mark — calculates supply correctly and subtracts to isolate usage cost. 1 mark — correct kWh to nearest unit. Common error: dividing $487.30 by 11 (→ GST component, not pre-GST).
2.1 — Brendan's full Managing Money (7 marks): sample Band-6 response with annotations
Sample Band-6 response.
(a) Taxable income.
Gross income = $94,400 + $820 + $1,640 = $96,860.
Allowable deductions = $560 + $1,140 + $300 = $2,000 (the $480 commute is excluded — home-to-regular-workplace travel is not deductible). [1 mark — correct identification + justification of excluded commute.]
∴ Taxable income = $96,860 − $2,000 = $94,860. [1 mark — correct taxable income.]
(b) Tax liability + refund/debt.
$94,860 in $45,001 – $120,000 bracket.
Income tax = $5,092 + 0.325 × ($94,860 − $45,000) = $5,092 + 0.325 × $49,860 = $5,092 + $16,204.50 = $21,296.50.
Medicare = $94,860 × 0.02 = $1,897.20.
∴ Total liability = $21,296.50 + $1,897.20 = $23,193.70. [1 mark — correct total liability.]
PAYG $23,800 > $23,193.70 → ∴ refund of $606.30. [1 mark — correct refund/debt with conclusion sentence.]
(c) Monthly budget and GST.
Monthly expenses: rent $2,180; groceries = $290 × 52 ÷ 12 ≈ $1,256.67; electricity = $568 ÷ 3 ≈ $189.33; phone $94; insurance = $1,680 ÷ 12 = $140.
∴ Total monthly expenses ≈ $2,180 + $1,256.67 + $189.33 + $94 + $140 = $3,860.00. [1 mark — correct conversions and total.]
After-tax annual income = $94,860 − $23,193.70 = $71,666.30. Monthly after-tax cash = $71,666.30 ÷ 12 ≈ $5,972.19.
∴ Monthly surplus = $5,972.19 − $3,860.00 = $2,112.19. [1 mark — correct monthly cash and surplus.]
GST component of electricity bill = $568 ÷ 11 ≈ $51.64. [1 mark — correct GST component using ÷11 on the GST-inclusive amount.]
Conclusion: Brendan has a comfortable monthly surplus of about $2,112, a refund of $606.30 from his tax return, and the GST embedded in his quarterly electricity bill is $51.64.
Total: 7/7.
Band descriptors for marker.
Band 3: Calculates taxable income and income tax but includes the commute as a deduction, OR omits Medicare. ≈ 3 marks.
Band 4: Taxable income, total liability and refund/debt all correct; monthly conversions attempted but at least one expense incorrectly converted. ≈ 4-5 marks.
Band 5: Full numerical solution but bare conclusions in (c) without sentences, OR uses ×0.10 for the GST component on an inclusive price. ≈ 6 marks.
Band 6: Complete: tax, liability, refund correctly chained, all monthly conversions correct, monthly surplus calculated, GST component using ÷11, AND a clear conclusion statement at the end. 7/7.