Dainika invested $2000 for three years at 4.4% per annum, compounding quarterly.
To earn the same amount of interest in three years in a simple interest account, the annual simple interest rate would need to be closest to
- 4.60%
- 4.68%
- 4.84%
- 4.98%
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Dainika invested $2000 for three years at 4.4% per annum, compounding quarterly.
To earn the same amount of interest in three years in a simple interest account, the annual simple interest rate would need to be closest to
\(B\)
\(FV\) | \(=2000\left(1-\dfrac{0.044}{4}\right)^{12}\) |
\(=$2280.57\) | |
\(\text{Interest pa}\) | \(=\dfrac{280.57}{3}=$93.52\) |
\(\text{SI rate}\) | \(=\dfrac{93.52}{2000}\times 100\%\) |
\(=4.676\dots\%\) |
\(\Rightarrow B\)
Twenty years ago, Hector invested a sum of money in an account earning interest at the rate of 3.2% per annum, compounding monthly.
After 10 years, he made a one-off extra payment of $10 000 to the account.
For the next 10 years, the account earned interest at the rate of 2.8% per annum, compounding monthly.
The balance of his account today is $686 904.09
The sum of money Hector originally invested is closest to
`B`
`text(Let)\ I = text(original investment)`
`text(Strategy 1:)`
`text(Balance)` | `= [I(1 + 3.2/(12 xx 100))^120 + 10\ 000](1 + 2.8/(12 xx 100))^120` |
`= $686\ 904.09` |
`text(Test each option in the equation)`
`text(Option)\ B:\ \ I = $370\ 000\ \ text(is correct)`
`text{Strategy 2 (By TVM Solver):}`
`N` | `=120` | |
`Itext{(%)}` | `= 2.8` | |
`PMT` | `=0` | |
`PV` | `= ?` | |
`FV` | `= 686\ 904.09` | |
`text(PY)` | `= text(CY) =12` |
`:. PV = 519\ 320.3`
`N` | `=120` | |
`Itext{(%)}` | `= 3.2` | |
`PMT` | `=0` | |
`PV` | `= ?` | |
`FV` | `= 509\ 320.3` | |
`text(PY)` | `= text(CY) =12` |
`:. PV = 370\ 000`
`=> B`
Gen invests $10 000 at an interest rate of 5.5% per annum, compounding annually.
After how many years will her investment first be more than double its original value?
`B`
`text(Find)\ n\ text(such that:)`
`10\ 000 xx 1.055^n` | `> 20\ 000` |
`1.055^n` | `> 2` |
`text(Testing some answer options:)`
`1.055^12 = 1.90`
`1.055^13 = 2.005`
`=> B`
Ray deposited $5000 in an investment account earning interest at the rate of 3% per annum, compounding quarterly.
A rule for the balance, `R_n` , in dollars, after `n` years is given by
`E`
`text(Quarterly rate) = 0.03/4 = 0.0075`
`text(Compounding periods) = 4n`
`:.\ text(Balance after)\ n\ text(years)`
`= 5000 xx 1.0075^(4n)`
`=> E`
The graph below shows the value, in dollars, of a compound interest investment after `n` compounding periods, `V_n`, for a period of four compounding periods.
The coordinates of the point where `n = 2` are `(2, b)`.
The value of `b` is
`C`
`text(Let)\ \ r = text(rate of interest)`
`V_0` | `= 500` |
`V_1` | `= V_0 xx (1 + r)^n` |
`580` | `= 500 (1 + r)^1` |
`1 + r` | `= 1.16` |
`r` | `= 16text(%)` |
`:. b` | `= 500 (1.16)^2` |
`= 672.80` |
`=> C`
Daniel borrows $5000, which he intends to repay fully in a lump sum after one year.
The annual interest rate and compounding period for five different compound interest loans are given below:
• Loan I – 12.6% per annum, compounding weekly
• Loan II – 12.8% per annum, compounding weekly
• Loan III – 12.9% per annum, compounding weekly
• Loan IV – 12.7% per annum, compounding quarterly
• Loan V – 13.2% per annum, compounding quarterly
When fully repaid, the loan that will cost Daniel the least amount of money is
`D`
`text(Weekly compounding loans ⇒ Loan I is cheaper)`
`text(Repayment of Loan I)` | `= 5000 xx (1 + 12.6/(52 xx 100))^52` |
`= $5670.55` |
`text(Quarterly compounding loans ⇒ Loan IV is cheaper)`
`text(Repayment of Loan IV)` | `= 5000 xx (1 + 2.7/(12 xx 100))^12` |
`= $5136.68` |
`:.\ text(Loan IV is cheapest.)`
`=> D`
Alex sends a bill to his customers after repairs are completed.
If a customer does not pay the bill by the due date, interest is charged.
Alex charges interest after the due date at the rate of 1.5% per month on the amount of an unpaid bill.
The interest on this amount will compound monthly.
Marcus paid the full amount one month after the due date.
How much did Marcus pay? (1 mark)
Alex sent Lily a bill of $428 for repairs to her car.
Lily did not pay the bill by the due date.
Let `A_n` be the amount of this bill `n` months after the due date.
How much interest was Lily charged?
Round your answer to the nearest cent. (1 mark)
a. | `text(Amount paid)` | `= 200 + 200 xx 1.5text(%)` |
`= 1.015 xx 200` | ||
`= $203` |
MARKER’S COMMENT: A recurrence relation has the initial value written first. Know why `A_n=428 xx 1.015^n` is incorrect.
b. `A_o = 428,qquadA_(n + 1) = 1.015A_n`
c. | `text(Total paid)\ (A_4)` | `= 1.015^4 xx 428` |
`= $454.26` |
`:.\ text(Total Interest)` | `= 454.26 – 428` |
`= $26.26\ \ (text(nearest cent))` |
The company prepares for this expenditure by establishing three different investments.
Determine the total value of this investment at the end of eight years. (2 marks)
Determine the total value of this investment at the end of eight years.
Write your answer correct to the nearest dollar. (1 mark)
Deposits of $200 are made to this account on the last day of each month after interest has been paid.
Determine the total value of this investment at the end of eight years.
Write your answer correct to the nearest dollar. (1 mark)
a. | `I` | `= (PrT)/100` |
`= (7000 xx 6.25 xx 8)/100` | ||
`= $3500` |
`:.\ text(Total value of investment)`
`= 7000 + 3500`
`= $10\ 500`
b. `text(Compounding periods) = 8 xx 4 = 32`
`text(Interest rate)` | `= (text(6%))/4` |
`= 1.5text(% per quarter)` |
`:.\ text(Total value of investment)`
`= PR^n`
`= 10\ 000(1.015)^32`
`= 16\ 103.24…`
`= $16\ 103\ \ text{(nearest $)}`
c. `text(By TVM Solver,)`
`N` | `= 8 xx 12 = 96` |
`I(text(%))` | `= 6.5` |
`PV` | `= 500` |
`PMT` | `= 200` |
`FV` | `= ?` |
`text(P/Y)` | `= text(C/Y) = 12` |
`=> FV = −25\ 935.30…`
`:.\ text(Total value of investment is $25 935.)`
It is estimated that inflation will average 2% per annum over the next eight years.
If a new machine costs $60 000 now, calculate the cost of a similar new machine in eight years time, adjusted for inflation. Assume no other cost change.
Write your answer correct to the nearest dollar. (1 mark)
`$70\ 300\ \ text{(nearest $)}`
`text(Find value)\ (A)\ text(in 8 years.)`
`A` | `= PR^n` |
`= 60\ 000(1.02)^8` | |
`= 70\ 299.562…` | |
`= $70\ 300\ \ text{(nearest $)}` |
Michelle decided to invest some of her money at a higher interest rate. She deposited $3000 in an account paying 8.2% per annum, compounding half yearly.
Write your answer correct to the nearest cent. (1 mark)
a. `text(Compounding periods)\ (n) = 2 xx 2 = 4`
`text(Interest per half year) = 8.2/2 = 4.1text(%)`
`:. A` | `= PR^n` |
`= 3000(1.041)^4` | |
`= 3523.093…` | |
`= $3523.09\ \ text{(nearest cent)}` |
b. `text(After 4 years)\ (n = 8),`
`A` | `= 3000(1.041)^8` |
`= 4137.396…` |
`:.\ text(Interest)` | `= 4137.396-3000` |
`= 1137.396…` | |
`= $1137.40\ \ text{(nearest cent)}` |
The golf club’s social committee has $3400 invested in an account which pays interest at the rate of 4.4% per annum compounding quarterly.
Write your answer in dollars correct to the nearest cent. (1 mark)
Write your answer in dollars correct to the nearest cent. (2 marks)
a. `text(Interest rate per quarter)`
`= 4.4/4`
`= 1.1text(% …as required.)`
b. `text(Compounding periods = 12)`
`A` | `= PR^n` |
`= 3400(1.011)^12` | |
`= 3876.973…` | |
`= $3876.97` |
c. `text(Compounding periods) = 6 xx 4 = 24`
`A` | `= 3400(1.011)^24` |
`= 4420.858…` |
`text(Interest earned over 6 years)`
`= 4420.86- 3400`
`= $1020.86\ \ text{(nearest cent)}`
Simple Saver is a simple interest investment in which interest is paid annually.
Growth Plus is a compound interest investment in which interest is paid annually.
Initially, $8000 is invested with both Simple Saver and Growth Plus.
The graph below shows the total value (principal and all interest earned) of each of these investments over a 15 year period.
The increase in the value of each investment over time is due to interest
Give a reason to justify your answer. (1 mark)
Find the amount of interest paid annually. (1 mark)
Write your answer as a percentage correct to one decimal place. (1 mark)
a. `text(Simple Saver has the highest annual)`
`text(interest rate because after 1 year,)`
`text(the value of investment is higher.)`
b. `text(Total interest earned)`
`= 21\ 800 – 8000`
`= $13\ 800`
`:.\ text(Interest paid annually)`
`= (13\ 800)/15`
`= $920`
c.i. `text(Using)\ A = PR^n,`
`24\ 000 = 8000 (1 + r/100)^15`
c.ii. | `(1 + r/100)^15` | `= 3` |
`1 + r/100` | `= 1.0759…` | |
`:. r` | `= 0.0759…` | |
`= 7.6text{% (1 d.p.)}` |
Tania purchased a house for $300 000.
She will have to pay stamp duty based on this purchase price.
Stamp duty rates are listed in the table below.
Write your answer to the nearest thousand dollars. (1 mark)
Tania bought her house at the start of 2011.
a. | `text(Stamp duty)` | `= 2870 + 6text(%) xx (300\ 000 – 130\ 000)` |
`= $13\ 070` |
b. `text(Using)\ \ \ A = PR^n`
`text(Value)` | `= 300\ 000(1.0317)^5` |
`= 350\ 661.7…` | |
`= $351\ 000\ \ text{(nearest $1000)}` |
c. `text(Find)\ n\ text(when)\ \ \ A > $450\ 000`
`300\ 000 xx 1.0317^n` | `= 450\ 000` |
`n` | `~~12.99…` |
`:.\ text(After 13 years, in 2024, the house value)`
`text(will be over)\ $450\ 000.`
A sponsor of the cricket club has invested $20 000 in a perpetuity.
The annual interest from this perpetuity is $750.
The interest from the perpetuity is given to the best player in the club every year, for a period of 10 years.
What is the expected price of this cricket equipment in 2015? (1 mark)
Write your answer, correct to the nearest dollar. (1 mark)
a. | `20\ 000 xx r` | `= 750` |
`:. r` | `= 750/(20\ 000)` | |
`= 0.0375` |
`:.\ text(Annual interest rate = 3.75%)`
b. `$20\ 000`
`text{(A perpetuity’s balance remains}`
`text{constant.)}`
c.i. `text(Expected price in 2015)`
`= 750 xx (1 + 3/100)`
`= 750 xx 1.03`
`= $772.50`
c.ii. `text(Value in 2014) xx (1.03)^10 = 750`
`:.\ text(Value in 2014)\ ` | `= 750/((1.03)^10)` |
`= 558.07…` | |
`= $558\ \ text{(nearest dollar)}` |
Mary invests $1200 for two years.
Interest is calculated at the rate of 3.35% per annum, compounding monthly.
The amount of interest she earns in two years is closest to
A. `$6.71`
B. `$40.82`
C. `$80.40`
D. `$81.75`
E. `$83.03`
`E`
`text(Monthly interest rate)\ = 3.35/12 = 0.27916…`
`text(Total after 2 years)` | `= 1200(1 + (0.27916…)/100)^24` |
`=$1283.03…` |
`:.\ text(Interest earned)` | `= 1283.03 – 1200` |
`= $83.03` |
`=> E`
An amount of $8000 is invested for a period of 4 years.
The interest rate for this investment is 7.2% per annum compounding quarterly.
The interest earned by the investment in the fourth year (in dollars) is given by
A. `4 xx (7.2/100 xx 8000)`
B. `8000 xx 1.018^4 - 8000 xx 1.018^3`
C. `8000 xx 1.018^16 - 8000 xx 1.018^12`
D. `8000 xx 1.072^4 - 8000 xx 1.072^3`
E. `8000 xx 1.072^16 - 8000 xx 1.072^12`
`C`
`text(4th year interest)` | `=\ text(Value after 4 years) -` |
`text(Value after 3 years.)` |
`text(Using)\ \ A = PR^n,`
`text(where)\ R = 1 + 7.2/(100 xx 4) = 1.018`
`text(Value after 4 years:)`
`A_4` | `= 8000 xx 1.018^((4 xx 4))` |
`= 8000 xx 1.018^(16)` |
`text(Value after 3 years:)`
`A_3` | `= 8000 xx 1.018^((4 xx 3))` |
`= 8000 xx 1.018^(12)` |
`:.\ text(4th year interest) = 8000 xx 1.018^(16) − 8000 xx 1.018^(12)`
`=> C`
Sam and Charlie each invest $5000 for three years.
Sam’s investment earns simple interest at the rate of 7.5% per annum.
Charlie’s investment earns interest at the rate of 7.5% per annum compounding annually.
At the conclusion of three years, correct to the nearest cent, Sam will have
A. $86.48 less than Charlie.
B. $86.48 more than Charlie.
C. $132.23 less than Charlie.
D. $132.23 more than Charlie.
E. the same as Charlie.
`A`
`text(Sam’s Investment,)`
`I` | `= (PrT)/100` |
`= ((5000)(7.5)(3))/100` | |
`= 1125` |
`:.\ text(Total amount)` | `= 5000 + 1125` |
`= $6125` |
`text(Charlie’s Investment,)`
`A` | `= PR^n` |
`= (5000)(1.075)^3` | |
`= $6211.48` |
`text(Difference)` | `= 6211.48-6125` |
`= $86.48` |
`=> A`
$10 000 is invested at a rate of 10% per annum compounding half yearly.
The value, in dollars, of this investment after five years, is given by
A. `10\ 000 xx 0.10 xx 5`
B. `10\ 000 xx 0.05 xx 10`
C. `10\ 000 xx 0.05^10`
D. `10\ 000 xx 1.05^10`
E. `10\ 000 xx 1.10^5`
`D`
`text(Interest rate)\ = \frac{10%}{2} = 5%\ \ \text{(per 6 months)}`
`text{Compounding periods}\ (n) =5 xx 2=10`
`:.A` | ` = PR^n` |
`= 10\ 000 xx 1.05^(10)` |
`=> D`
The points on the graph below show the balance of an investment at the start of each quarter for a period of six years.
The same rate of interest applied for these six years.
In relation to this investment, which one of the following statements is true?
A. interest is compounding annually and is credited annually
B. interest is compounding annually and is credited quarterly
C. interest is compounding quarterly and is credited quarterly
D. simple interest is paid on the opening balance and is credited annually
E. simple interest is paid on the opening balance and is credited quarterly
`A`
`text(From the graph, as balance increases after)`
`text(each year, interest is credited annually.)`
`:.\ text(Eliminate)\ B, C\ text(and)\ E.`
`text(The difference of the balances between successive)`
`text(years is increasing which indicates that interest is)`
`text(compounding.)`
`:.\ text(Eliminate)\ D.`
`=> A`
Tim invests $3000 in a term deposit account that adds 6.5% interest annually, calculated on the account balance at the end of each year.
The interest paid in the fourth year is
A. `$195.00`
B. `$221.16`
C. `$235.55`
D. `$3623.85`
E. `$3859.40`
`C`
`text(Using)\ \ A = PR^n`
`text(Total after 3rd year)` | `= 3000(1.065)^3 \ \ \ \ \ (n =3)` |
`= $3623.848875…` | |
`= $3623.85 \ \ (text(2 d.p.))` | |
`text(Total after 4th year)` | `= 3000(1.065)^4 \ \ \ \ \ (n = 4)` |
`= $3859.399…` | |
`= $3859.40 \ \ (text(2 d.p.))` |
`:.\ text(Interest paid in 4th year)` | `= 3859.40 − 3623.85` |
`= $235.55` |
`=> C`
Anthony invested $15 000 in an account. It earned `rtext(%)` interest per annum, compounding monthly.
The amount of interest that is earned in the third year of the investment is given by
A. `15\ 000 (1 + r / 1200)^3 - 15\ 000 (1 + r / 1200)^2`
B. `15\ 000 (1 + r / 1200)^36 - 15\ 000 (1 + r / 1200)^24`
C. `15\ 000 (1 + r / 100)^3 - 15\ 000 (1 + r / 100)^2`
D. `15\ 000 (1 + r / 100)^36 - 15\ 000 (1 + r / 100)^24`
E. `15\ 000 (1 + r / 1200)^4 - 15\ 000 (1 + r / 1200)^3`
`B`
`text(Interest in 3rd year)`
`=\ text(Value after 3 yrs) – text(Value after 2 years)`
`text(Using)\ \ A = PR^n,\ \ text(where)\ \ A = 15\ 000, and`
`R` | `= (1 + r / {12 xx 100})` |
`= (1 + r / 1200)` |
`text(In first 3 years:)`
`A_3` | `= 15\ 000 (1 + r / 1200)^(12 xx 3)` |
`= 15\ 000 (1 + r / 1200)^36` |
`text(In first 2 years:)`
`A_2` | `= 15\ 000 (1 + r / 1200)^(12 xx 2)` |
`= 15\ 000 (1 + r / 1200)^24` |
`:.\ text(Interest in 3rd year)`
`= 15\ 000 (1 + r/1200)^36 – 15\ 000 (1 + r/1200)^24`
`=> B`
An amount of $22 000 is invested for three years at an interest rate of 3.5% per annum, compounding annually.
The value of the investment at the end of three years is closest to
A. `$2310`
B. `$9433`
C. `$24\ 040`
D. `$24\ 392`
E. `$31\ 433`
`D`
`P = 22\ 000,\ \ R = 1.035,\ \ n = 3`
`A` | `=PR^n` |
`= 22\ 000 xx 1.035^3` | |
`= 24\ 391.79…` |
`=> D`
$15 000 is invested for 12 months.
For the first six months the interest rate is 6.1% per annum compounding monthly
After six months the interest rate increases to 6.25% per annum compounding monthly.
The total interest earned by this investment over 12 months is closest to
A. $926
B. $935
C. $941
D. $953
E. $965
`D`
`text(Using)\ \ A = PR^n,`
`text(Value after the 1st 6 months)`
`= 15\ 000 xx (1 + 6.1 / {12 xx 100})^6`
`=$15\ 463.35…`
`text(Value after the 2nd 6 months)`
`=15\ 463.35… xx (1 + 6.25 / {12 xx 100})^6`
`=$15\ 952.91…`
`:.\ text(Interest)` | `= 15\ 952.91 – 15\ 000` |
`= $952.91` |
`=> D`
The transaction details for a savings account for the month of July 2012 are shown below.
Interest is calculated and paid monthly on the minimum monthly balance.
The annual rate of interest paid on this account is closest to
A. `3.5text(%)`
B. `4.3text(%)`
C. `4.7text(%)`
D. `4.9text(%)`
E. `5.2text(%)`
`E`
`text(Interest) = 21.99`
`text(Minimum balance) = 5101.82`
`text{Rate of interest (monthly)}` | `= 21.99 / 5101.82` |
`= 0.0043…` |
`:.\ text(Yearly rate of interest)`
`= 0.0043… xx 12`
`= 0.0517…`
`= 5.17text(%)`
`=> E`
$10 000 is invested for five years. Interest is earned at a rate of 8% per annum, compounding quarterly.
Which one of the following calculations will give the total interest earned, in dollars, by this investment?
A. `10\ 000 xx 1.02^5-10\ 000`
B. `10\ 000 xx 1.02^20-10\ 000`
C. `10\ 000 xx 1.08^5 -10\ 000`
D. `10\ 000 xx 1.08^20-10\ 000`
E. `10\ 000 xx 1.02^20`
`B`
`text{Quarterly interest rate (R)} = 8/4=2%=0.02`
`text(5 years)\ =5 xx4=20\ text(quarters),\ \ n=20`
`text(Using)\ A = PR^n,`
`A` | `=10\ 000 xx (1 + 0.02)^20` |
`=10\ 000xx (1.02)^20` |
`:.\ text(Interest)` | `=\ text(Final amount) – text(original investment)` |
`= 10\ 000 xx 1.02^20 – 10\ 000` |
`=> B`
Amy invests $15 000 for 150 days.
Interest is calculated at the rate of 4.60% per annum, compounding daily.
Assuming that there are 365 days in a year, the value of her investment after 150 days is closest to
A. `$15\ 279`
B. `$15\ 284`
C. `$15\ 286`
D. `$15\ 690`
E. `$16\ 776`
`C`
`text(Annual rate)` | `= 4.60text(%)` |
`text(Daily rate)` | `= (4.60text{%})/365=0.046/365` |
`text(Using)\ \ A = PR^n`
`text(where)\ R` | `= 1 + 0.0460/365` |
`= 1.0001260…` |
`:.\ text(Investment)` | `= 15\ 000 xx (1.0001260…)^150` |
`= 15\ 000 xx 1.01908…` | |
`= $15\ 286.24` |
`=> C`