Question

How much simple interest would 1000 earn in 275 days at an interest rate of 4.21%

Answer 1

Now, there are 365 (excluding leap years) in a year, so, 275 days is not even a year, but is  275/365 of a year, or 55/73 of a year.

$\bf \qquad \textit{Simple Interest Earned}\\\\ I = Prt\qquad \begin{cases} I=\textit{interest earned}\\ P=\textit{original amount deposited}\to& \ 1000\\ r=rate\to 4.21\%\to \frac{4.21}{100}\to &0.0421\\ t=years\to \frac{275}{365}\to &\frac{55}{73} \end{cases} \\\\\\ I=1000\cdot 0.0421\cdot \cfrac{55}{73}$