Final answer:
The interest rate on this loan is not 18.4 percent. To calculate the true interest rate, we need to use the formula for compound interest. The interest rate is approximately 17.92 percent and rounded to the nearest 0.125 percent, it is 18 percent. The effective annual rate (EAR) is approximately 19.56 percent.
Step-by-step explanation:
The interest rate on this loan is not 18.4 percent.
To calculate the true interest rate, we need to use the formula for compound interest:
![\[ A = P \left(1 + (r)/(n)\right)^(nt) \]](https://img.qammunity.org/2024/formulas/business/high-school/uotb50mnfel9dwecmb8uu95z6g2hl2eej6.png)
Where:
A symbolizes the final amount after time t
P symbolizes the principal amount borrowed
r symbolizes the annual interest rate (as a decimal)
n symbolizes the number of times interest is compounded per year
t symbolizes the time in years
In this case, we know that A = $23,680, P = $20,000, t = 1 year, and n = 12 (monthly compounding).
Using the formula, we can solve for r (the interest rate):
![\[ 23,680 = 20,000 \left(1 + (r)/(12)\right)^(12) \]](https://img.qammunity.org/2024/formulas/business/high-school/k4eahxzsitzc50yk5fwy7z8qbhr7lui6dh.png)
Simplifying this equation, we find that the interest rate is approximately 17.92 percent.
To legally quote the interest rate, the finance company would have to round this rate to the nearest 0.125 percent, which would be 18 percent.
The effective annual rate (EAR) takes into account the effects of compounding. To calculate the EAR, we can use the formula:
![\[ \text{EAR} = \left(1 + (r)/(n)\right)^n - 1 \]](https://img.qammunity.org/2024/formulas/business/high-school/d456s5um14hm1hjjoj70d5rnjfqxfq3lcs.png)
This formula calculates the actual annual interest rate when interest is compounded more frequently than annually.
Using the values from the original loan, the EAR would be approximately 19.56 percent.