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HSC Mathematics Standard 2 financial mathematics (2026 guide)

HSCMaths Standard 2Study guide22 min read

Quick answer

HSC Maths Standard 2 financial mathematics is the highest-yield topic in the paper: drill compound interest, loans and annuities until they are automatic, always convert annual rates to per-period rates, and round only at the final answer.

Jump to a section
  1. Compound interest
  2. Depreciation
  3. Shares and dividends
  4. Inflation and CPI
  5. Credit cards
  6. Reducing-balance loans
  7. Annuities and superannuation
  8. Exam strategy
  9. Common traps across the topic
  10. Check your knowledge

Reducing-balance mortgage: annual payment split into interest and principal portions across 30 years A stacked area chart for a 30-year reducing-balance mortgage of dollar 650,000 at 6 percent per annum compounded monthly. The total annual repayment is constant at about dollar 46,765, shown as a dashed horizontal line. Each year's payment splits into an interest portion (lower band, accent colour) and a principal portion (upper band, light fill). In year 1 the interest portion is about dollar 38,800 and the principal portion is about dollar 8,000. The interest band shrinks every year while the principal band grows; by year 30 the interest portion is about dollar 1,500 and the principal portion is about dollar 45,300. Year axis from 0 to 30 in 5-year increments. Dollar axis from 0 to 50,000 in 10,000 increments. 0 5 10 15 20 25 30 $10k $20k $30k $40k $50k Year of the loan annual payment ($) total annual payment M ≈ $46,765 (constant) interest portion principal portion year 1: interest ≈ $38,800 year 30: interest ≈ $1,500 Example loan $650k at 6% p.a., monthly, 30 years

Figure 1. Stacked area chart of a 30-year reducing-balance mortgage (650,000650{,}000 at 6%6\% per annum compounded monthly, monthly repayment ≈$3,897\approx \$3{,}897). The total annual repayment MM stays constant. In early years almost all of each payment goes to interest; in later years almost all goes to principal. Total interest paid over 30 years is roughly $753,000\$753{,}000.

Financial mathematics is the single largest source of marks in the HSC Mathematics Standard 2 paper. Expect about 2020-3030 marks out of 100100 across the two sections, often split across 44-55 questions in Section II. Most of these questions are predictable in structure: you are given a financial scenario and asked to apply a formula from the reference sheet to find a future value, a repayment, an interest amount, or a comparison.

The good news is that the topic rewards drilling. Once the formulas are automatic, financial maths questions take less time per mark than almost anything else in the paper. The bad news is that small errors (wrong per-period rate, wrong rounding) cascade and can lose you most of a multi-part question.

This guide covers every part of the syllabus topic: compound interest, depreciation, shares, inflation, credit cards, reducing-balance loans, and annuities. Every formula is on the NESA reference sheet, so this guide focuses on application: when to use what, how to read worded problems, and the common errors that cost marks.

Compound interest

The compound interest formula:

FV=PV(1+r)n.FV = PV (1 + r)^n.

The crucial step is to convert the nominal annual rate to a per-period rate. Match the period to the compounding frequency:

  • Annual: r=Rr = R, n=n = years.
  • Monthly: r=R/12r = R/12, n=12×n = 12 \times years.
  • Quarterly: r=R/4r = R/4, n=4×n = 4 \times years.
  • Daily: r=R/365r = R/365, n=365×n = 365 \times years.

To find the present value (today's amount that grows to FVFV):

PV=FV(1+r)n.PV = \frac{FV}{(1 + r)^n}.

To solve for time:

n=log⁡(FV/PV)log⁡(1+r).n = \frac{\log(FV / PV)}{\log(1 + r)}.

To solve for rate:

r=(FVPV)1/n−1.r = \left(\frac{FV}{PV}\right)^{1/n} - 1.

Present value of a first-home deposit goal

A first-home buyer wants $120,000\$120{,}000 in 55 years for a deposit. Their high-interest savings account pays 4.5%4.5\% per annum compounded monthly. How much do they need to invest today as a single lump sum?

Step 1. Identify the formula and the unknown.

We know the future value, the rate and the term. We want the present value. The present-value form of the compound interest formula is what we want.

PV=FV(1+r)n PV = \frac{FV}{(1 + r)^n}

Step 2. Convert the nominal annual rate to a per-period (monthly) rate.

Compounding is monthly, so rr must be the rate per month and nn the number of months.

  • r=0.045/12=0.00375r = 0.045 / 12 = 0.00375 per month.
  • n=5×12=60n = 5 \times 12 = 60 months.

Step 3. Compute the growth factor (1+r)n(1 + r)^n.

This is the multiplier that turns today's money into the deposit amount.

(1.00375)60≈1.25181 (1.00375)^{60} \approx 1.25181

Step 4. Divide the future value by the growth factor.

PV=120,0001.25181≈95,860.40 PV = \frac{120{,}000}{1.25181} \approx 95{,}860.40

Step 5. State the answer with currency and units.

Answer. About $95,860.40\$95{,}860.40 needs to be invested today to grow to $120,000\$120{,}000 in 55 years. The gap between this and the family's available savings is what they would have to top up with regular deposits (an annuity calculation).

Depreciation

Two methods.

Straight-line: a fixed dollar amount each year. V=P−DnV = P - D n. If a salvage value SS is given for nendn_{\text{end}} years, D=(P−S)/nendD = (P - S) / n_{\text{end}}.

Declining-balance: a fixed percentage each year. V=P(1−r)nV = P(1 - r)^n. The multiplier 1−r1 - r is the per-year factor.

The two methods give different values at any year. Declining-balance gives a higher book value early on but never reaches zero. Straight-line gives a constant drop and hits salvage on schedule.

Comparing straight-line and declining-balance on a new Toyota Hilux

A new Toyota Hilux costs $56,000\$56{,}000. Compare a declining-balance schedule at 25%25\% per year against a straight-line schedule over 88 years with a $8000\$8000 salvage value, and find the value at the end of year 55 under each method.

Step 1. Write down the formula for each method.

Both formulas are on the NESA reference sheet.

  • Declining: V=P(1−r)nV = P(1 - r)^n, with P=56,000P = 56{,}000 and 1−r=0.751 - r = 0.75.
  • Straight-line: V=P−DnV = P - D n, with P=56,000P = 56{,}000 and D=(P−S)/nend=(56,000−8000)/8=6000D = (P - S)/n_{\text{end}} = (56{,}000 - 8000)/8 = 6000 per year.

Step 2. Compute the year-55 value under declining-balance.

We raise the multiplier 0.750.75 to the power 55, then multiply by PP.

Vdecl=56,000×0.755=56,000×0.23730≈13,289 V_{\text{decl}} = 56{,}000 \times 0.75^5 = 56{,}000 \times 0.23730 \approx 13{,}289

Step 3. Compute the year-55 value under straight-line.

Subtract 55 years of $6000\$6000 depreciation from PP.

VSL=56,000−6000×5=56,000−30,000=26,000 V_{\text{SL}} = 56{,}000 - 6000 \times 5 = 56{,}000 - 30{,}000 = 26{,}000

Step 4. Build a comparison table for a few key years to see the shape.

Year Declining (V=56000(0.75)nV = 56000 (0.75)^n) Straight-line (V=56000−6000nV = 56000 - 6000 n)
11 $42,000\$42{,}000 $50,000\$50{,}000
33 $23,625\$23{,}625 $38,000\$38{,}000
55 $13,289\$13{,}289 $26,000\$26{,}000
88 $5,608\$5{,}608 $8,000\$8{,}000

Answer. At year 55, declining-balance gives about $13,289\$13{,}289 and straight-line gives $26,000\$26{,}000. Declining drops faster early; straight-line lands exactly on the salvage value at year 88. The ATO publishes effective lives for many asset classes and depreciation must match the ATO's allowed method for tax purposes.

Shares and dividends

Three calculations:

  • Dividend yield = (dividend per share / share price) ×100%\times 100\%.
  • Capital gain = number of shares ×\times (selling price −- purchase price).
  • Total return ($) = total dividends + capital gain.
  • Total return (%) = (total return) / (original investment) ×100%\times 100\%.

A typical Australian bank share might trade at $98\$98 and pay an annual dividend of $4.80\$4.80, giving a yield of about 4.9%4.9\%.

Inflation and CPI

The Consumer Price Index, published quarterly by the ABS, measures the price of a typical household basket of goods and services.

  • Inflation between two years: CPI2−CPI1CPI1×100%\frac{CPI_2 - CPI_1}{CPI_1} \times 100\%.
  • Annual compound rate: (CPI2/CPI1)1/n−1(CPI_2 / CPI_1)^{1/n} - 1.
  • Convert old dollars to new: amount ×CPInew/CPIold\times CPI_{\text{new}} / CPI_{\text{old}}.

Approximate CPI from ABS (catalogue 6401.0):

  • June 2014: 105.9105.9.
  • June 2019: 114.8114.8.
  • June 2024: 138.8138.8.

So $1\$1 in June 2014 has the same purchasing power as $138.8/105.9≈$1.31\$138.8 / 105.9 \approx \$1.31 in June 2024. Over the decade, annual inflation averaged about 2.7%2.7\%.

Credit cards

Credit cards compound interest daily. The per-day rate is R/365R / 365. The compound formula gives the balance after nn days:

A=P(1+R/365)n.A = P(1 + R/365)^n.

A typical Australian card rate in 2025 is 18%18\%-22%22\% per annum, much higher than typical mortgage rates. The interest-free period means that if you pay the full balance by the due date, no interest is charged. If even $1\$1 is left unpaid, the back-dating rule usually means interest applies from the original purchase date on the entire balance.

Paying only the minimum (typically 2%2\% of the balance, or a fixed dollar minimum) barely reduces the principal because most of the payment goes to interest. A $5000\$5000 balance paid only at the 2%2\% minimum takes roughly 2020 years to clear.

Reducing-balance loans

The recurrence model: Bn=Bn−1(1+r)−MB_n = B_{n-1}(1 + r) - M, with B0=PB_0 = P.

The closed form for the outstanding balance:

Bn=P(1+r)n−M⋅(1+r)n−1r.B_n = P(1 + r)^n - M \cdot \frac{(1 + r)^n - 1}{r}.

To find the repayment that fully repays the loan in nn periods:

M=Pr1−(1+r)−n.M = \frac{P r}{1 - (1 + r)^{-n}}.

Each payment splits into interest and principal:

  • Ik=r⋅Bk−1I_k = r \cdot B_{k-1}.
  • Pk=M−IkP_k = M - I_k.

Early payments are mostly interest; later payments are mostly principal.

Typical Sydney mortgage repayment (monthly compounding)

A young Sydney couple borrows $650,000\$650{,}000 at 6%6\% per annum compounded monthly over 3030 years. Find the monthly repayment, total amount paid and total interest.

Step 1. Convert annual rate and term to per-period units.

Compounding is monthly, so the rate must be per month and nn must be the number of monthly periods.

  • r=0.06/12=0.005r = 0.06 / 12 = 0.005 per month.
  • n=30×12=360n = 30 \times 12 = 360 months.

Step 2. Compute the discount factor (1+r)−n(1 + r)^{-n}.

This factor appears in the denominator of the repayment formula and is the only computational step that genuinely needs a calculator.

(1.005)−360≈0.16604 (1.005)^{-360} \approx 0.16604

So 1−(1.005)−360≈0.833961 - (1.005)^{-360} \approx 0.83396.

Step 3. Apply the repayment formula M=Pr1−(1+r)−nM = \dfrac{P r}{1 - (1 + r)^{-n}}.

This is the rearrangement of the present-value-of-annuity formula. Multiply principal by per-period rate, divide by the factor above.

M=650,000×0.0050.83396=32500.83396≈3896.79 M = \frac{650{,}000 \times 0.005}{0.83396} = \frac{3250}{0.83396} \approx 3896.79

Step 4. Compute the total amount paid and the total interest.

Multiply monthly repayment by total number of payments, then subtract the original principal.

  • Total paid: 360×3896.79≈$1,402,845360 \times 3896.79 \approx \$1{,}402{,}845.
  • Total interest: $1,402,845−$650,000≈$752,845\$1{,}402{,}845 - \$650{,}000 \approx \$752{,}845.

Step 5. Stress-test against a small rate rise.

If the rate rises to 6.5%6.5\% (one 0.5%0.5\% rate hike on the RBA cash rate), repeat steps 11-33 with r=0.0054167r = 0.0054167. The monthly repayment jumps to about $4109\$4109, a $212\$212 per month increase.

Answer. Monthly repayment about $3896.79\$3896.79. Total paid over 3030 years about $1.40\$1.40 million. Total interest about $752,845\$752{,}845 - roughly 116%116\% of the original principal. The mortgage-stress sensitivity to rate changes (about $212\$212 extra per month per 0.5%0.5\% rate hike) is exactly why the RBA cash rate dominates household budget news.

Outstanding balance after partway through a car loan

A couple takes out a $32,000\$32{,}000 car loan at 7.2%7.2\% per annum compounded monthly over 55 years. They make the standard repayment for 2424 months and then ask the bank for the balance still owing so they can refinance. Find the monthly repayment and the balance after 2424 months.

Step 1. Convert to per-period units.

  • r=0.072/12=0.006r = 0.072 / 12 = 0.006 per month.
  • n=5×12=60n = 5 \times 12 = 60 months.

Step 2. Apply the repayment formula to find MM.

(1.006)−60≈0.69892  ⟹  1−(1.006)−60≈0.30108 (1.006)^{-60} \approx 0.69892 \implies 1 - (1.006)^{-60} \approx 0.30108

M=32,000×0.0060.30108=1920.30108≈637.71 M = \frac{32{,}000 \times 0.006}{0.30108} = \frac{192}{0.30108} \approx 637.71

Step 3. Use the closed-form balance formula after n=24n = 24 months.

Bn=P(1+r)n−M⋅(1+r)n−1r B_n = P(1 + r)^n - M \cdot \frac{(1 + r)^n - 1}{r}

This says: grow the original principal forward by nn periods, then subtract the future value of all the repayments already made.

Step 4. Compute each piece.

  • (1.006)24≈1.15440(1.006)^{24} \approx 1.15440.
  • Principal grown forward: 32,000×1.15440≈36,940.8032{,}000 \times 1.15440 \approx 36{,}940.80.
  • Future-value-of-annuity factor: (1.15440−1)/0.006≈25.7333(1.15440 - 1)/0.006 \approx 25.7333.
  • Future value of repayments: 637.71×25.7333≈16,412.41637.71 \times 25.7333 \approx 16{,}412.41.

Step 5. Subtract to find the outstanding balance.

B24≈36,940.80−16,412.41≈20,528.39 B_{24} \approx 36{,}940.80 - 16{,}412.41 \approx 20{,}528.39

Answer. Monthly repayment about $637.71\$637.71. After 2424 months, balance still owing is about $20,528\$20{,}528. Notice that out of the $15,305\$15{,}305 paid so far (24×637.7124 \times 637.71), only about $11,472\$11{,}472 went to principal - the rest ($3833\$3833) was interest. That is the front-loaded interest pattern of every reducing-balance loan.

Annuities and superannuation

The future-value-of-annuity formula:

FV=M⋅(1+r)n−1r.FV = M \cdot \frac{(1 + r)^n - 1}{r}.

Applied to superannuation: MM is the per-period contribution, rr is the per-period interest rate, nn is the number of contributions.

Graduate superannuation balance at age 6565

A graduate aged 2525 earns $70,000\$70{,}000 per year. The Super Guarantee is 11.5%11.5\% for 2024-25 (rising to 12%12\% from 1 July 2025). Assume contributions are paid quarterly and the fund earns 7%7\% per annum compounded quarterly. What balance can they expect at age 6565?

Step 1. Compute the per-quarter contribution.

The annual SG amount is 11.5%11.5\% of salary; we then split into four quarters.

  • Annual SG: $70,000×0.115=$8050\$70{,}000 \times 0.115 = \$8050.
  • Per-quarter: $8050/4=$2012.50\$8050 / 4 = \$2012.50.

Step 2. Convert the annual return to a per-quarter rate, and find nn.

  • r=0.07/4=0.0175r = 0.07 / 4 = 0.0175 per quarter.
  • n=40 years×4=160n = 40 \text{ years} \times 4 = 160 quarters.

Step 3. Compute the growth factor (1+r)n(1 + r)^n.

(1.0175)160≈16.0142 (1.0175)^{160} \approx 16.0142

Step 4. Apply the future-value-of-annuity formula.

This formula adds up all 160160 contributions, each compounded forward to age 6565.

FV=2012.50⋅16.0142−10.0175=2012.50⋅857.95≈1,726,637 FV = 2012.50 \cdot \frac{16.0142 - 1}{0.0175} = 2012.50 \cdot 857.95 \approx 1{,}726{,}637

Step 5. Sanity-check and answer.

Total contributions are only 160×2012.50=$322,000160 \times 2012.50 = \$322{,}000, so the rest (about $1.4\$1.4 million) is investment growth. That dominance of compound interest over 4040 years is exactly why super matters.

Answer. About $1.73\$1.73 million in super at age 6565, before considering wage rises over 4040 years (which would increase contributions and the final balance significantly).

Present value of an annuity: lump sum needed to fund regular withdrawals

A retiree wants to draw $60,000\$60{,}000 at the end of each year for 2525 years from an account earning 5%5\% per annum compounded annually. How much do they need in the account today?

Step 1. Identify the formula.

The present-value-of-annuity formula on the reference sheet gives the lump sum today that funds a stream of equal future withdrawals.

PV=M⋅1−(1+r)−nr PV = M \cdot \frac{1 - (1 + r)^{-n}}{r}

Step 2. Plug in the per-period rate, the term and the withdrawal.

Compounding is annual, so r=0.05r = 0.05 and n=25n = 25 years. The withdrawal is M=60,000M = 60{,}000.

Step 3. Compute the discount factor.

(1.05)−25≈0.29530  ⟹  1−(1.05)−25≈0.70470 (1.05)^{-25} \approx 0.29530 \implies 1 - (1.05)^{-25} \approx 0.70470

Step 4. Compute the annuity factor and the present value.

1−(1.05)−250.05≈0.704700.05≈14.0939 \frac{1 - (1.05)^{-25}}{0.05} \approx \frac{0.70470}{0.05} \approx 14.0939

PV≈60,000×14.0939≈845,635 PV \approx 60{,}000 \times 14.0939 \approx 845{,}635

Step 5. State the answer with currency.

Answer. The retiree needs about $845,635\$845{,}635 in the account today. They will withdraw $1.5\$1.5 million in total (25×$60,00025 \times \$60{,}000); the extra comes from continued compound growth on the unwithdrawn balance.

Comparing two investment options with different compounding frequencies

A saver compares two banks for a $25,000\$25{,}000 deposit held for 44 years.

  • Bank A: 5.2%5.2\% per annum compounded annually.
  • Bank B: 5.0%5.0\% per annum compounded monthly.

Which option gives the higher future value, and by how much?

Step 1. Set up the compound interest formula for each option.

The formula FV=PV(1+r)nFV = PV(1 + r)^n applies in both cases, but the per-period rate and the number of periods change with the compounding frequency.

  • Bank A: r=0.052r = 0.052, n=4n = 4.
  • Bank B: r=0.05/12≈0.0041667r = 0.05 / 12 \approx 0.0041667, n=4×12=48n = 4 \times 12 = 48.

Step 2. Compute the growth factor and future value for Bank A.

(1.052)4≈1.22504 (1.052)^{4} \approx 1.22504

FVA=25,000×1.22504≈30,626 FV_A = 25{,}000 \times 1.22504 \approx 30{,}626

Step 3. Compute the growth factor and future value for Bank B.

(1.0041667)48≈1.22090 (1.0041667)^{48} \approx 1.22090

FVB=25,000×1.22090≈30,523 FV_B = 25{,}000 \times 1.22090 \approx 30{,}523

Step 4. Take the difference and answer.

FVA−FVB≈30,626−30,523≈103FV_A - FV_B \approx 30{,}626 - 30{,}523 \approx 103.

Answer. Bank A gives about $103\$103 more after 44 years, even though its annual rate is only 0.20.2 percentage points higher than Bank B's. The lesson: the headline rate dominates the compounding frequency over short horizons, but only because 0.20.2 percentage points exceeds the boost from monthly versus annual compounding at these rates.

Exam strategy

For financial mathematics:

  • Term 1. Drill compound interest until conversion to per-period rate is automatic.
  • Term 2. Drill reducing-balance loans and amortisation tables.
  • Term 3. Drill annuities and superannuation. Make sure you can solve for both the future value and the required payment.
  • Term 4. Past papers. Aim for 44-55 full papers under timed conditions before the HSC.

The single most common error is using the annual rate with monthly periods (or vice versa). Always check: per-period rate matches the compounding frequency, and number of periods matches the time span in those same units.

Common traps across the topic

Wrong rate frequency
0.06/120.06 / 12, not 0.060.06, when compounding is monthly.
Mixing simple and compound
Read carefully whether the question says "simple" or "compound".
Wrong formula for the situation
Loans use the present-value-of-annuity rearrangement. Savings use the future-value-of-annuity formula. Single-lump-sum investments use plain compound interest.
Rounding too early
Carry intermediate values to 55-66 decimal places. Round only at the final answer.
Forgetting units
All financial answers end in dollars (and cents). State the currency and decimals.

Check your knowledge

Try these before checking the worked solutions. They mirror the spread of question types you will see in Section II.

  1. $8000\$8000 is invested at 4%4\% per annum compounded annually for 66 years. Find the future value.
  2. What is the per-period rate, and the number of periods, if a 55-year loan compounds quarterly at 8%8\% per annum?
  3. A machine costs $24,000\$24{,}000 and depreciates by the declining-balance method at 20%20\% per annum. Find its book value after 44 years.
  4. The CPI in June 2019 was 114.8114.8 and in June 2024 it was 138.8138.8. Find the average annual inflation rate over the five-year period.
  5. A loan of $15,000\$15{,}000 is repaid at 4%4\% per annum compounded monthly with $300\$300 per month. Use the recurrence Bn=Bn−1(1+r)−MB_n = B_{n-1}(1 + r) - M with r=0.04/12r = 0.04/12 to find the balance owing immediately after the third repayment.
  6. Find the monthly repayment on a $400,000\$400{,}000 home loan at 6%6\% per annum compounded monthly over 2525 years.
  7. Sam pays $300\$300 at the end of each month into a savings account earning 4.8%4.8\% per annum compounded monthly for 1010 years. What is the future value?
  8. A retiree has $500,000\$500{,}000 in an account earning 4%4\% per annum compounded annually. They wish to draw an equal amount at the end of each year for 2020 years until the account empties. What annual withdrawal does the account support?
Solutions to check-your-knowledge questions

These eight questions cover compound interest (annual and quarterly), declining-balance depreciation, inflation, iterative loan balances, monthly repayments, future value of an annuity, and present value of an annuity. The key habit throughout is converting the annual rate to the per-period rate before substituting.

Step 1: Q1. Compound interest with annual compounding

Use FV=PV(1+r)nFV = PV(1 + r)^n with PV=8000PV = 8000, r=0.04r = 0.04, and n=6n = 6 years.

FV=8000×(1.04)6≈8000×1.26532≈10,122.55 FV = 8000 \times (1.04)^6 \approx 8000 \times 1.26532 \approx 10{,}122.55

After 66 years the balance is about $10,122.55\$10{,}122.55.

Step 2: Q2. Convert annual rate for quarterly compounding

Quarterly compounding means the per-period rate is the annual rate divided by 44, and the total number of periods is years multiplied by 44.

r=0.084=0.02 per quarter,n=5×4=20 quartersr = \frac{0.08}{4} = 0.02 \text{ per quarter}, \qquad n = 5 \times 4 = 20 \text{ quarters}

These are the values to substitute into the compound-interest formula for the next calculation.

Step 3: Q3. Declining-balance depreciation after 4 years

The declining-balance formula is V=P(1−r)nV = P(1 - r)^n. Here P=24,000P = 24{,}000, r=0.20r = 0.20, and n=4n = 4.

V=24,000×(0.8)4=24,000×0.4096=9830.40 V = 24{,}000 \times (0.8)^4 = 24{,}000 \times 0.4096 = 9830.40

Book value after 44 years is $9830.40\$9830.40.

Step 4: Q4. Average annual inflation rate from CPI figures

The average annual growth rate between two index values over nn years is found by taking the nn-th root of their ratio and subtracting 1.

(138.8114.8)1/5−1≈(1.20906)0.2−1≈1.03879−1≈0.0388 \left(\frac{138.8}{114.8}\right)^{1/5} - 1 \approx (1.20906)^{0.2} - 1 \approx 1.03879 - 1 \approx 0.0388

Average inflation ≈3.88%\approx 3.88\% per year.

Step 5: Q5. Iterative loan balance over three months

Use r=0.04/12≈0.003333r = 0.04 / 12 \approx 0.003333 and monthly repayment M=300M = 300. Multiply the opening balance by (1+r)(1 + r) and subtract MM at the end of each period.

B1=15,000×1.003333−300≈14,750.00B_1 = 15{,}000 \times 1.003333 - 300 \approx 14{,}750.00

B2=14,750.00×1.003333−300≈14,499.17B_2 = 14{,}750.00 \times 1.003333 - 300 \approx 14{,}499.17

B3=14,499.17×1.003333−300≈14,247.50B_3 = 14{,}499.17 \times 1.003333 - 300 \approx 14{,}247.50

Balance after the third repayment is about $14,247.50\$14{,}247.50.

Step 6: Q6. Monthly repayment on a $400{,}000 mortgage

Use the loan repayment formula M=Pr1−(1+r)−nM = \dfrac{Pr}{1 - (1 + r)^{-n}} with r=0.005r = 0.005 (monthly) and n=300n = 300 months (25 years).

(1.005)−300≈0.22397  ⟹  1−(1.005)−300≈0.77603 (1.005)^{-300} \approx 0.22397 \implies 1 - (1.005)^{-300} \approx 0.77603

M=400,000×0.0050.77603=20000.77603≈2577.21 M = \frac{400{,}000 \times 0.005}{0.77603} = \frac{2000}{0.77603} \approx 2577.21

Monthly repayment is about $2577.21\$2577.21.

Step 7: Q7. Future value of Sam's regular deposits

Use FV=M⋅(1+r)n−1rFV = M \cdot \dfrac{(1 + r)^n - 1}{r} with monthly deposit M=300M = 300, rate r=0.048/12=0.004r = 0.048/12 = 0.004, and n=120n = 120 months.

(1.004)120≈1.61602 (1.004)^{120} \approx 1.61602

FV=300⋅1.61602−10.004=300×154.0050≈46,201.50 FV = 300 \cdot \frac{1.61602 - 1}{0.004} = 300 \times 154.0050 \approx 46{,}201.50

Sam ends with about $46,201.50\$46{,}201.50. Total contributions are 300×120=$36,000300 \times 120 = \$36{,}000 and the rest ($10,201.50\$10{,}201.50) is interest earned.

Step 8: Q8. Annual withdrawal from a retirement fund

Rearrange the present-value-of-annuity formula to find the regular withdrawal MM, using PV=500,000PV = 500{,}000, r=0.04r = 0.04, and n=20n = 20 years.

M=PV⋅r1−(1+r)−n=500,000×0.041−(1.04)−20 M = \frac{PV \cdot r}{1 - (1 + r)^{-n}} = \frac{500{,}000 \times 0.04}{1 - (1.04)^{-20}}

(1.04)−20≈0.45639  ⟹  1−(1.04)−20≈0.54361 (1.04)^{-20} \approx 0.45639 \implies 1 - (1.04)^{-20} \approx 0.54361

M=20,0000.54361≈36,787.71 M = \frac{20{,}000}{0.54361} \approx 36{,}787.71

Final answer: the retiree can draw about $36,787.71\$36{,}787.71 at the end of each year for 2020 years before the account empties.

Sources & how we know this

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