## Precalculus (6th Edition) Blitzer

Let us assume, $A$ is the total amount, $P$ is the principal amount, $r$ is the rate of interest, and $t$ is the number of years. Therefore, \begin{align} & A=\18,000\\&P=\6000\\&n=10\end{align} And the interest rate can be computed using the formula: \begin{align} & A=P{{e}^{rt}} \\ & 18,000=6000{{e}^{10r}} \\ & {{e}^{10r}}=3 \\ & r=0.1099 \end{align} Therefore, the percentage rate of interest is: $r=10.99$ %