linda deposits $90,000 into an account that pays 4% interest per year, compounded annually. bob deposits…

linda deposits $90,000 into an account that pays 4% interest per year, compounded annually. bob deposits $90,000 into an account that also pays 4% per year. but it is simple interest. find the interest linda and bob earn during each of the first three years. then decide who earns more interest for each year. assume there are no withdrawals and no additional deposits.
Answer
Explanation:
Step1: Calculate Bob's simple - interest formula
The simple - interest formula is $I = Prt$, where $P$ is the principal amount, $r$ is the annual interest rate (in decimal form), and $t$ is the time in years. Given $P=$90000$, $r = 0.04$, and $t$ varies for each year.
Step2: Calculate Linda's compound - interest formula
The compound - interest formula is $A=P(1 + r)^t$, and the interest earned $I=A - P=P((1 + r)^t-1)$. For $P = 90000$ and $r = 0.04$.
First - year calculations
Bob's interest
$I_{Bob1}=Prt=90000\times0.04\times1 = 3600$.
Linda's interest
$I_{Linda1}=90000\times((1 + 0.04)^1-1)=90000\times(1.04 - 1)=90000\times0.04 = 3600$. They earn the same amount in the first year.
Second - year calculations
Bob's interest
$I_{Bob2}=Prt=90000\times0.04\times1 = 3600$.
Linda's interest
$A_{Linda2}=90000\times(1 + 0.04)^2=90000\times1.0816$, $I_{Linda2}=90000\times1.0816-90000=90000\times(1.0816 - 1)=90000\times0.0816 = 3744$. Linda earns more in the second year.
Third - year calculations
Bob's interest
$I_{Bob3}=Prt=90000\times0.04\times1 = 3600$.
Linda's interest
$A_{Linda3}=90000\times(1 + 0.04)^3=90000\times1.124864$, $I_{Linda3}=90000\times1.124864-90000=90000\times(1.124864 - 1)=90000\times0.124864 = 3901.92$. Linda earns more in the third year.
Answer:
| Year | Interest Linda earns (Interest compounded annually) | Interest Bob earns (Simple Interest) | Who earns more interest? |
|---|---|---|---|
| First | $$3600$ | $$3600$ | They earn the same amount. |
| Second | $$3744$ | $$3600$ | Linda earns more. |
| Third | $$3901.92$ | $$3600$ | Linda earns more. |