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NSWMaths Standard 2Syllabus dot point

What is the present value of an annuity, and how do future value and present value annuity tables let you find or back-solve a contribution?

Use future value and present value annuity tables, and calculate the present value of an annuity

The HSC Maths Standard 2 dot point on annuity tables and present value. What the present value of an annuity is, the link PV = FV / (1+r)^n, reading future-value and present-value annuity tables at the period by rate intersection, back-solving a contribution or rate from a table, converting an annual rate to the per-period row, and a loan as the present value of its repayments.

Generated by Claude Opus 4.814 min answer

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What this dot point is asking

NESA wants you to do two related things. First, understand and calculate the present value of an annuity: the single lump sum today that is worth exactly the same as a stream of equal future payments. Second, read annuity factor tables. There are two, the future-value-of-11 table and the present-value-of-11 table. You find the value where the right period row and rate column meet, then multiply it by the contribution. You also need to back-solve from a table for a required contribution or interest rate. This is the table partner to the future-value formula. The formula gives one answer; the table gives a whole grid of ready-made answers you simply read off.

The answer

Money has a time value. A dollar you will get in three years is worth less than a dollar in your hand today, because today's dollar can be banked to earn interest. The present value of an annuity uses that idea on a whole stream of payments. (An annuity is a series of equal payments made at regular times.) It asks a simple question: if I am promised an equal payment at the end of every period for nn periods, what single amount today is worth the same? You find the answer by discounting each future payment back to today, that is, working out what it is worth now, and then adding the results. The diagram below does this for four yearly payments of $9000 at 6%6\%. Each future $9000 shrinks as it is pulled back to the present, and the four shrunken amounts add up to a single present value of $31,186.

Present value of an annuity: four future payments discounted back to today A timeline with payments of 9000 dollars at the end of years 1, 2, 3 and 4. Each payment is discounted back to the present at 6 percent per annum, shrinking to 8,491, 8,010, 7,557 and 7,129 dollars. The four present values are summed into a single lump sum today of about 31,186 dollars, the present value of the annuity. now 1 2 3 4 end of year $9000 PV $8,491 $9000 PV $8,010 $9000 PV $7,557 $9000 PV $7,129 $31,186 present value

Present value of a single payment, then of a whole stream

Everything here is built on one rearrangement of the compound interest formula. A lump sum PVPV invested now grows to FV=PV(1+r)nFV = PV(1 + r)^n. Make PVPV the subject:

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

This is discounting: dividing a future amount by (1+r)n(1 + r)^n to find what it is worth today. For example, $10,000 due in 33 years at 5%5\% per annum is worth 100001.053=100001.1576258638.38\dfrac{10000}{1.05^3} = \dfrac{10000}{1.157625} \approx 8638.38, i.e. $8638.38 today, because that amount banked now at 5%5\% would grow back to $10,000.

The present value of an annuity just applies this to every payment in the stream and adds them up. If a payment MM falls at the end of each of nn periods, the payment kk periods away is worth M(1+r)k\dfrac{M}{(1 + r)^k} today, so

PV=M(1+r)+M(1+r)2++M(1+r)n.PV = \frac{M}{(1 + r)} + \frac{M}{(1 + r)^2} + \cdots + \frac{M}{(1 + r)^n}.

That is a geometric series, a sum where each term is a fixed multiple of the one before. Just as the future-value series folds up into a neat formula, so does this one. You are not expected to add it up by hand in the exam, because the table does it for you. But seeing it as "the sum of each payment discounted back to today" is what makes a table answer make sense, rather than feel like magic.

A loan is the present value of its repayments

The clearest place this idea shows up is a loan. When a bank lends you money today, the amount it hands over is exactly the present value of all the repayments you promise to make. The lender is happy with this, because those future repayments, discounted at the loan rate, are worth exactly what they gave you now. So for a reducing-balance loan (one paid off by equal instalments),

amount borrowed=(present-value factor)×repayment per period.\text{amount borrowed} = \text{(present-value factor)} \times \text{repayment per period}.

That one sentence lets you back-solve a repayment straight from a present-value table: just divide the amount borrowed by the table factor. It is the same method as a savings goal, only read in the other direction. That is why the present-value table and reducing-balance loans are two views of one idea.

Two tables, one method

There are two annuity tables and they are easy to confuse, so fix the difference firmly.

  • The future value of 11 table answers: if I pay in $1 at the end of each period, how much have I accumulated by the end? The factor is (1+r)n1r\dfrac{(1 + r)^n - 1}{r}. These factors are bigger than nn (interest has been added on).
  • The present value of 11 table answers: a stream of $1 payments at the end of each period is worth how much as a single amount today? The factor is 1(1+r)nr\dfrac{1 - (1 + r)^{-n}}{r}. These factors are smaller than nn (future money is discounted down).

The procedure is identical for both: find the row for the number of periods, the column for the rate per period, read the factor at the intersection, and multiply by the contribution. The only decision is which table, and that is decided by the word "today" or "now" (present value) versus "after nn periods", "accumulated" or "final balance" (future value).

Here are small tables for $1, with the factors computed to 44 decimal places. First the future value of $1 at the end of each period:

Period 2%2\% 4%4\% 6%6\% 8%8\% 10%10\% 12%12\%
11 1.00001.0000 1.00001.0000 1.00001.0000 1.00001.0000 1.00001.0000 1.00001.0000
22 2.02002.0200 2.04002.0400 2.06002.0600 2.08002.0800 2.10002.1000 2.12002.1200
33 3.06043.0604 3.12163.1216 3.18363.1836 3.24643.2464 3.31003.3100 3.37443.3744
44 4.12164.1216 4.24654.2465 4.37464.3746 4.50614.5061 4.64104.6410 4.77934.7793
55 5.20405.2040 5.41635.4163 5.63715.6371 5.86665.8666 6.10516.1051 6.35286.3528
66 6.30816.3081 6.63306.6330 6.97536.9753 7.33597.3359 7.71567.7156 8.11528.1152

And the present value of $1 paid at the end of each period:

Period 2%2\% 4%4\% 6%6\% 8%8\% 10%10\% 12%12\%
11 0.98040.9804 0.96150.9615 0.94340.9434 0.92590.9259 0.90910.9091 0.89290.8929
22 1.94161.9416 1.88611.8861 1.83341.8334 1.78331.7833 1.73551.7355 1.69011.6901
33 2.88392.8839 2.77512.7751 2.67302.6730 2.57712.5771 2.48692.4869 2.40182.4018
44 3.80773.8077 3.62993.6299 3.46513.4651 3.31213.3121 3.16993.1699 3.03733.0373
55 4.71354.7135 4.45184.4518 4.21244.2124 3.99273.9927 3.79083.7908 3.60483.6048
66 5.60145.6014 5.24215.2421 4.91734.9173 4.62294.6229 4.35534.3553 4.11144.1114

Notice the first row of the future-value table is all 1.00001.0000: a single payment at the end of period 11 in a 11-period annuity earns no interest, so $1 paid is $1 accumulated. In the present-value table the first row is the plain one-period discount factor 11+r\dfrac{1}{1 + r}, for example 11.06=0.9434\dfrac{1}{1.06} = 0.9434 at 6%6\%.

Converting an annual rate to the per-period row

Tables are labelled by the rate and the count per period, not per year. So when interest is added more than once a year (called sub-annual compounding), you must convert before you read the table, exactly as you do with the formula. Divide the yearly rate by the number of compounding periods in a year to get the column. Multiply the number of years by that same number to get the row.

  • Yearly contributions, yearly compounding: column =R= R, row == years.
  • Quarterly: column =R/4= R/4, row =4×= 4 \times years.
  • Monthly: column =R/12= R/12, row =12×= 12 \times years.

So $2000 per quarter for 11 year at 8%8\% per annum compounded quarterly is read at column 8%÷4=2%8\% \div 4 = 2\% and row 4×1=44 \times 1 = 4, not at 8%8\% and 11. Getting this conversion wrong is the most common table error, because the headings tempt you to read the yearly figures straight off.

How exam questions ask about present value and tables

The wording is the whole game. Each phrasing points at one table and one operation. Learn to translate:

  • "What single amount today is equivalent to..." or "What lump sum must be invested now to provide..." A present-value question: read the present-value table and multiply, PV=factor×MPV = \text{factor} \times M.
  • "What will the account be worth after nn years / at the end of the term?" A future-value question: read the future-value table and multiply.
  • "Use the table to find the future value of an annuity of $X..." Straight table read: convert to the per-period row and column, read the factor, multiply by XX.
  • "Find the payment / contribution per period of an annuity whose present value (or future value) is $X." Back-solve: divide the target by the table factor, because target=factor×M\text{target} = \text{factor} \times M means M=targetfactorM = \dfrac{\text{target}}{\text{factor}}.
  • "$A invested at the end of each year for nn years grows to $B. Find the interest rate." Read across a row: compute the factor you need as BA\dfrac{B}{A}, then look along the period-nn row of the future-value table for the column whose factor matches.
  • "How much can be borrowed if the repayment is $R per period..." A loan is the present value of its repayments: amount borrowed =present-value factor×R= \text{present-value factor} \times R. Reverse it to find the repayment from a known loan.

Edge case: which table when the question gives you both numbers

Some questions hand you a future value and ask for a present value, or vice versa, to see whether you discount or accumulate. Anchor on the timeline. If the money you are given sits at the end of the term and you are asked for an equivalent amount now, you are discounting, so use the present-value table (or divide a future value by (1+r)n(1 + r)^n for a single sum). If you are given regular contributions and asked for the final balance, you are accumulating, so use the future-value table. The two tables are linked: the present value of an annuity grown forward for nn periods equals its future value, since PV×(1+r)n=FVPV \times (1 + r)^n = FV. In the pension example, $31,185.95 grown at 6%6\% for 44 years gives 31185.95×1.064=39371.5431185.95 \times 1.06^4 = 39371.54, which is exactly the future value of the same $9000 annuity, 9000×4.3746=39371.549000 \times 4.3746 = 39371.54.

Edge case: tables only go so far

A printed table has a fixed set of rows and columns. Sometimes a question needs a rate or a period the table does not list, like a 7%7\% column when the table jumps from 6%6\% to 8%8\%, or period 3030 when it stops at 66. Then the table cannot answer it and you must fall back on the formula. NESA picks table questions so the period and rate you need land on the grid. So if your converted row or column is not in the table, recheck the conversion before assuming you need the formula. The table and the formula always agree where both apply, because the table is just the formula worked out ahead of time for common values.

Exam-style practice questions

Practice questions written in the style of NESA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

2021 HSC-style (table-style)3 marksA retiree will draw $9600 at the end of each year for 77 years from a fund earning 4%4\% per annum compounded annually. Using the present-value-of-11 annuity table, find the single amount that must be in the fund today.
Show worked answer →

The present value of the annuity is the lump sum today that is equivalent to the stream of future withdrawals.

Read the present-value-of-11 table at period 77, rate 4%4\%: the factor is 6.00216.0021.

PV=6.0021×9600=57619.72PV = 6.0021 \times 9600 = 57619.72, i.e. $57619.72.

Markers reward selecting the present-value (not future-value) table, reading the correct intersection, multiplying by the contribution, and rounding to cents.

2022 HSC-style (table-style)3 marksAn annuity has a present value of $33240 at 6%6\% per annum compounded annually for 33 years. Using the present-value-of-11 annuity table, find the payment per period.
Show worked answer →

Read the present-value-of-11 table at period 33, rate 6%6\%: the factor is 2.67302.6730.

The present value equals the factor times the payment, so 33240=2.6730×PMT33240 = 2.6730 \times \text{PMT}.

Divide: PMT=332402.673012435.47\text{PMT} = \dfrac{33240}{2.6730} \approx 12435.47, i.e. about $12435.

Markers reward writing PV=factor×PMTPV = \text{factor} \times \text{PMT}, dividing the target by the table factor, and rounding sensibly.

Practice questions

Original practice questions graded from foundation to exam level, each with a full worked solution. Try them before revealing the solution.

foundation1 marksAn annuity will pay $5000 at the end of each year for 33 years, with money worth 4%4\% per annum compounded annually. Using the present-value-of-11 annuity table, the factor at period 33, rate 4%4\% is 2.77512.7751. Find the present value of the annuity.
Show worked solution →
Choose the operation
A present value is wanted from a stream of payments, so multiply the table factor by the payment.
Use the given factor
Compounding is annual, so the factor is the one read at period 33, rate 4%4\%, namely 2.77512.7751.
Multiply by the payment
The present value is the factor times the annual payment.

PV=2.7751×5000=13875.50.PV = 2.7751 \times 5000 = 13875.50.

State the answer. Answer: the present value of the annuity is $13,875.50.

foundation2 marksA retiree will draw a pension of $7500 at the end of each year for 44 years from a fund earning 6%6\% per annum compounded annually. Using the present-value-of-11 annuity table, find the single amount that must be in the fund today.
Show worked solution →
Choose the table
The phrase "single amount today" signals present value, so use the present-value-of-11 table.
Read the factor at the intersection
Compounding is annual, so the column is 6%6\% and the row is period 44. The factor is 3.46513.4651.
Multiply by the payment
The present value is the factor times the annual draw.

PV=3.4651×7500=25988.25.PV = 3.4651 \times 7500 = 25988.25.

State the answer. About $25,988.25 must be in the fund today. Check. Discounting each payment by hand gives 75001.06+75001.062+75001.063+75001.064=7075.47+6674.97+6297.14+5940.70=25988.29\dfrac{7500}{1.06} + \dfrac{7500}{1.06^2} + \dfrac{7500}{1.06^3} + \dfrac{7500}{1.06^4} = 7075.47 + 6674.97 + 6297.14 + 5940.70 = 25988.29, matching the table to a few cents of rounding.

foundation2 marksMia invests $4000 at the end of each year into an account paying 10%10\% per annum compounded annually, for 33 years. Using the future-value-of-11 annuity table, find the balance at the end of the term.
Show worked solution →
Choose the table
"Balance at the end of the term" signals future value, so use the future-value-of-11 table.
Read the factor
Compounding is annual, so the column is 10%10\% and the row is period 33. The factor is 3.31003.3100.
Multiply by the contribution
The future value is the factor times the annual payment.

FV=3.3100×4000=13240.00.FV = 3.3100 \times 4000 = 13240.00.

State the answer. The balance is $13,240.00. Check. The total paid in is 3×4000=120003 \times 4000 = 12000, i.e. $12,000.00, so the interest earned is 1324012000=124013240 - 12000 = 1240, i.e. $1240.00, which is positive as it must be for an account that earns interest.

foundation2 marksSam pays $6000 into an account at the end of each year for 22 years at 12%12\% per annum compounded annually. Using the future-value-of-11 annuity table, the factor at period 22, rate 12%12\% is 2.12002.1200. Find the balance at the end of the term.
Show worked solution →
Choose the operation
A final balance is wanted from regular payments, so multiply the future-value factor by the contribution.
Use the given factor
Compounding is annual, so the factor read at period 22, rate 12%12\% is 2.12002.1200.
Multiply by the contribution
The future value is the factor times the annual payment.

FV=2.1200×6000=12720.00.FV = 2.1200 \times 6000 = 12720.00.

State the answer. Answer: the balance at the end of the term is $12,720.00.

core3 marksA fund must provide a payment of $11\,000 at the end of each year for 55 years to a beneficiary, with the fund earning 8%8\% per annum compounded annually. Using the present-value-of-11 annuity table, find the single amount needed in the fund today.
Show worked solution →
Choose the table
The payments fall in the future and a single amount is wanted now, so this is a present value: use the present-value-of-11 table.
Read the factor
Compounding is annual, so the column is 8%8\% and the row is period 55. The factor is 3.99273.9927.
Multiply by the payment
The present value is the factor times the annual payment.

PV=3.9927×11000=43919.70.PV = 3.9927 \times 11000 = 43919.70.

State the answer. About $43,919.70 is needed in the fund today. Check. The total drawn over the five years is 5×11000=550005 \times 11000 = 55000, i.e. $55,000.00, and the present value $43,919.70 is sensibly less than this, because future money is discounted back to today.

core3 marksPriya invests $1500 at the end of each quarter into an account paying 8%8\% per annum compounded quarterly, for 11 year. Using the future-value-of-11 annuity table, find the balance at the end of the year and the interest earned.
Show worked solution →
Convert to the per-period row and column
Compounding is quarterly, so the column is 8%÷4=2%8\% \div 4 = 2\% and the row is 4×1=44 \times 1 = 4 quarters, not column 8%8\% and row 11.
Read the factor
At period 44, rate 2%2\%, the future-value factor is 4.12164.1216.
Multiply by the contribution
The future value is the factor times the quarterly payment.

FV=4.1216×1500=6182.40.FV = 4.1216 \times 1500 = 6182.40.

Find the interest. The total paid in is 4×1500=60004 \times 1500 = 6000, i.e. $6000.00, so the interest is 6182.406000=182.406182.40 - 6000 = 182.40.

State the answer. The balance is $6182.40, including $182.40 of interest. Check. Reading the unconverted row 11 at 8%8\% would give a factor of 1.00001.0000 and a balance of only $1500, which is clearly too small for four deposits, confirming the conversion to row 44, column 2%2\% was needed.

core3 marksThe Lee family wants $40\,000 in 55 years for a house deposit, saving an equal amount at the end of each year into an account paying 6%6\% per annum compounded annually. Using the future-value-of-11 annuity table, find the annual contribution required.
Show worked solution →
Set up the table relationship
The future value equals the future-value factor times the unknown payment, FV=factor×MFV = \text{factor} \times M, so to find the payment you divide.
Read the factor
Compounding is annual, so the column is 6%6\% and the row is period 55. The future-value factor is 5.63715.6371.
Divide the target by the factor
Rearranging 40000=5.6371×M40000 = 5.6371 \times M for MM gives

M=400005.63717095.85.M = \frac{40000}{5.6371} \approx 7095.85.

State the answer. The family must save about $7095.85 at the end of each year. Check. Multiplying back, 5.6371×7095.85400005.6371 \times 7095.85 \approx 40000, recovering the target, so the division was set up correctly.

core3 marksA retirement fund must pay an equal amount at the end of each year for 66 years to a member, and the fund earns 10%10\% per annum compounded annually. The single amount in the fund today is $25\,000. Using the present-value-of-11 annuity table, the factor at period 66, rate 10%10\% is 4.35534.3553. Find the annual payment the fund can provide.
Show worked solution →
See the relationship
The single amount today is the present value of the payment stream, so PV=factor×PMTPV = \text{factor} \times \text{PMT}, and the payment is found by dividing.
Use the given factor
Compounding is annual, so the present-value factor is the one at period 66, rate 10%10\%, namely 4.35534.3553.
Divide the present value by the factor
Rearranging 25000=4.3553×PMT25000 = 4.3553 \times \text{PMT} for the payment gives

PMT=250004.35535740.13.\text{PMT} = \frac{25000}{4.3553} \approx 5740.13.

State the answer. Answer: the fund can pay about $5740.13 at the end of each year. Check. Multiplying back, 4.3553×5740.13250004.3553 \times 5740.13 \approx 25000, recovering the present value, so the division was set up correctly.

exam4 marksJordan borrows $28\,000 for a car at 6%6\% per annum compounded annually and repays it in equal instalments at the end of each year for 66 years. Using the present-value-of-11 annuity table, find the annual repayment, and hence the total interest paid over the life of the loan.
Show worked solution →
See the loan as a present value
The amount borrowed is the present value of the repayment stream, so amount borrowed=present-value factor×repayment\text{amount borrowed} = \text{present-value factor} \times \text{repayment}, and the repayment is found by dividing.
Read the factor
Compounding is annual, so the column is 6%6\% and the row is period 66. The present-value-of-11 factor is 4.91734.9173.
Divide the loan by the factor
Rearranging 28000=4.9173×R28000 = 4.9173 \times R for the repayment RR gives

R=280004.91735694.18.R = \frac{28000}{4.9173} \approx 5694.18.

Find the total interest. Over 66 years the total repaid is 6×5694.18=34165.086 \times 5694.18 = 34165.08, i.e. about $34,165.08, so the interest is 34165.0828000=6165.0834165.08 - 28000 = 6165.08, about $6165.08.

State the answer. Jordan repays about $5694.18 at the end of each year, paying about $6165.08 in interest in total. (Using the unrounded factor gives a repayment of about $5694.15; the few cents difference is table rounding.) Check. The total repaid $34,165.08 exceeds the $28,000 borrowed, as it must for a loan that charges interest.

exam3 marksAn annuity of $12\,500 invested at the end of each year for 33 years grows to a future value of $40\,580. Using the future-value-of-11 annuity table, find the annual interest rate.
Show worked solution →

Compute the factor you need. Since FV=factor×MFV = \text{factor} \times M, the required factor is the future value divided by the contribution.

factor=4058012500=3.2464.\text{factor} = \frac{40580}{12500} = 3.2464.

Match the factor along the period-33 row
Scan the row for period 33 in the future-value table for the column whose factor is 3.24643.2464. The 6%6\% column is 3.18363.1836, the 8%8\% column is 3.24643.2464, and the 10%10\% column is 3.31003.3100.
Read off the rate
The exact match is the 8%8\% column.
State the answer
The annuity earns 8%8\% per annum. Check. Reading forwards at 8%8\%, 3.2464×12500=405803.2464 \times 12500 = 40580, which is the given future value, confirming the rate.
exam4 marksAn annuity has a present value of $30\,000 at 12%12\% per annum compounded annually for 44 years. Using the present-value-of-11 annuity table, find the payment per period.
Show worked solution →
Identify the table and operation
A present value is given and the payment is wanted, so use the present-value-of-11 table and back-solve, since PV=factor×PMTPV = \text{factor} \times \text{PMT} means you divide.
Read the factor
Compounding is annual, so the column is 12%12\% and the row is period 44. The present-value-of-11 factor is 3.03733.0373.
Divide the present value by the factor
Rearranging 30000=3.0373×PMT30000 = 3.0373 \times \text{PMT} for the payment gives

PMT=300003.03739877.19.\text{PMT} = \frac{30000}{3.0373} \approx 9877.19.

State the answer. The payment per period is about $9877.19. Check. Multiplying back, 3.0373×9877.19300003.0373 \times 9877.19 \approx 30000, recovering the present value, so the back-solve was set up correctly.

exam5 marksAisha saves $3000 at the end of each year for 55 years into an account paying 8%8\% per annum compounded annually. From the annuity tables, the future-value-of-11 factor at period 55, rate 8%8\% is 5.86665.8666, and the present-value-of-11 factor at the same intersection is 3.99273.9927. (a) Find the balance at the end of the 55 years and the total interest earned. (b) Find the single amount Aisha could instead invest today to provide the same future balance, and confirm it is the present value of the annuity.
Show worked solution →

Part (a): choose the future-value table. A final balance from regular savings means future value, so multiply the future-value factor by the contribution.

FV=5.8666×3000=17599.80.FV = 5.8666 \times 3000 = 17599.80.

The total paid in is 5×3000=150005 \times 3000 = 15000, i.e. $15,000.00, so the interest earned is 17599.8015000=2599.8017599.80 - 15000 = 2599.80.

Part (a) answer. The balance is $17,599.80, including $2599.80 of interest.

Part (b): use the present-value table. The lump sum today equivalent to the same stream is the present value of the annuity, found by multiplying the present-value factor by the payment.

PV=3.9927×3000=11978.10.PV = 3.9927 \times 3000 = 11978.10.

Confirm the link. Growing this present value forward for 55 years gives 11978.10×1.08517599.7611978.10 \times 1.08^5 \approx 17599.76, matching the balance in part (a) to a few cents of table rounding, so it is indeed the present value of the annuity.

Part (b) answer. Answer: (a) the balance is $17,599.80 with $2599.80 interest; (b) the equivalent single amount today is $11,978.10, the present value of the annuity.

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