Answer :
Given:
Monthly charge = $40
Loan amount = $840
Let's find the annual interest rate.
To find the annual interest rate, apply the Simple interest formula.
[tex]r=\frac{100\ast interest}{\text{Principal}\times time}[/tex]Where:
r is the rate
Interest is the store charge = $40
Principal is the loan amount = $840
Here, the time is 1 month.
Let's convert thr time to years, where 1 year = 12 months.
1 month = 1/12 year
Thus, we have:
[tex]\begin{gathered} r=\frac{100\times40}{840\times\frac{1}{12}} \\ \\ r=\frac{100\times40}{840\times0.83} \\ \\ r=\frac{4000}{70} \\ \\ r=\text{ 57.14\%} \end{gathered}[/tex]Therefore, the annual interest rate is 57.14%
ANSWER:
57.14%