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\$8,100 is invested in an account earning [tex]3.7\%[/tex] interest (APR), compounded daily.

1. Write a function showing the value of the account after [tex]t[/tex] years. Round all coefficients in the function to four decimal places.
2. Determine the percentage of growth per year (APY), to the nearest hundredth of a percent.

Function: [tex]f(t) = \square \, ( ) \, \square[/tex]


Sagot :

Let's break this question into two parts: constructing the function and calculating the annual percentage yield (APY).

### Step 1: Constructing the Function Showing the Value of the Account

We know the investment is $8100, the annual interest rate (APR) is 3.7%, and the interest is compounded daily.

1. Initial investment [tex]\( P \)[/tex]:
[tex]\[ P = 8100 \][/tex]

2. Annual interest rate (APR):
[tex]\[ r = 3.7\% = 0.037 \][/tex]

3. Number of times the interest is compounded per year:
[tex]\[ n = 365 \][/tex]

The formula for the value of an investment compounded [tex]\( n \)[/tex] times per year is:
[tex]\[ A(t) = P \left(1 + \frac{r}{n}\right)^{nt} \][/tex]

Substituting the known values:
[tex]\[ A(t) = 8100 \left(1 + \frac{0.037}{365}\right)^{365t} \][/tex]

Next, we need to round the coefficients to four decimal places:

Let’s denote:
[tex]\[ 1 + \frac{0.037}{365} = 1 + 0.0001014 \approx 1.0001 \][/tex]

Therefore, the function [tex]\( f \)[/tex] showing the value of the account after [tex]\( t \)[/tex] years is:
[tex]\[ f(t) = 8100 \times 1.0001^{365t} \][/tex]

### Step 2: Determining the APY (Annual Percentage Yield)

APY is the effective annual rate. It can be calculated using the formula:
[tex]\[ APY = \left(1 + \frac{r}{n}\right)^n - 1 \][/tex]

Substituting the known values:
[tex]\[ APY = \left(1 + \frac{0.037}{365}\right)^{365} - 1 \][/tex]

Upon calculation and rounding to the nearest hundredth of a percent:
[tex]\[ APY \approx 3.77\% \][/tex]

### Final Answer
The function showing the value of the account after [tex]\( t \)[/tex] years, with coefficients rounded to four decimal places, is:
[tex]\[ f(t) = 8100 \times 1.0001^{365t} \][/tex]

The percentage of growth per year (APY) to the nearest hundredth of a percent is:
[tex]\[ 3.77\% \][/tex]