Simple interest formula:
A = P(1 + rt)
where A is the final amount, P is the principal, r is the interest rate (as a decimal), and t is time.
Given that t is in years, then r will be the annual interest rate.
Substituting with A = 6864, P = 6000, and t = 5, we get:
[tex]\begin{gathered} 6864=6000\cdot(1+r\cdot5) \\ \frac{6864}{6000}=1+r\cdot5 \\ 1.144-1=r\cdot5 \\ \frac{0.144}{5}=r \\ 0.0288=r \end{gathered}[/tex]The annual interest rate is 0.0288 or 2.88%
