The <em>simple annual interest</em> rate for the $ 525 loan is equal to 46.35 %.
<h3>What is the interest rate behind a pay back?</h3>
In this situation we assume that the loan does not accumulate interests continuously in time. Hence, the <em>interest</em> rate for paying the loan back 75 days later is:
575 = 525 · (1 + r/100)
50 = 525 · r /100
5000 = 525 · r
r = 9.524
The loan has an <em>interest</em> rate of 9.524 % for 75 days. <em>Simple annual interest</em> rate is determine by rule of three:
r' = 9.524 × 365/75
r' = 46.350
The <em>simple annual interest</em> rate for the $ 525 loan is equal to 46.35 %.
