Can someone please prove to me that $I = PRT$, where $P$ is the principal, $R$ is the interest rate, and $T$ is the number of years/time. I have seen $I = P(1+TR) = P+PTR$ which does not equal $PRT$, so I am slightly confused. Any help is appreciated, Thanks!
You have for simple interest at a fixed interest rate per time period $R$:
Where $I$ is the total interest after $T$ time periods. Therefore your other formula should read:
Where $P(T)$ is the principle after $T$ time periods.