Answer :
The formula to calculate the simple interest rate is:
[tex]R=(\frac{1}{T})(\frac{A}{P}-1)[/tex]Where R is the simple interest rate (in decimal form), T is the time, P is the principal (the initial amount borrowed) and A is the total amount paid after time T. In this case:
[tex]\begin{gathered} T=7 \\ A=720 \\ P=660 \end{gathered}[/tex]Substituting these values into the formula:
[tex]R=(\frac{1}{7})(\frac{720}{660}-1)[/tex]Solving the operations:
[tex]R=\frac{1}{7}(0.09090909)[/tex][tex]R=0.012987[/tex]To convert this simple interest rate into a percentage, we multiply it by 100:
[tex]0.012987\times100=1.2987[/tex]This is the simple interest rate per month:
R=1.2987 % per moth
We can also calculate the simple interest rate per year by multiplying the previous result by 12 (this is because there are 12 months in a year)
[tex]1.2987\times12=15.5844[/tex]The simple interest rate per year is:
R=15.5844 % per year
Answer:
R=1.2987 % per moth
R=15.5844 % per year