The principal $\mathrm{P}$ is borrowed and the loan's future value $\mathrm{A}$ at time $\mathrm{t}$ is given. Determine the loan's simple interest rate $\mathrm{r}$. \[ P=\$ 9000.00, A=\$ 11430.00, t=3 \text { years } \] $\%$ (Round to the nearest tenth of a percent as needed.)

Step 1 ：The principal P is borrowed and the loan's future value A at time t is given. We are asked to determine the loan's simple interest rate r. The given values are P = $9000.00, A = $11430.00, and t = 3 years.

Step 2 ：The formula for simple interest is given by: \(A = P(1 + rt)\), where A is the future value of the loan, P is the principal amount (the initial amount of money), r is the annual interest rate (in decimal form), and t is the time the money is invested for (in years).

Step 3 ：We can rearrange this formula to solve for r: \(r = \frac{A - P}{Pt}\)

Step 4 ：Substitute the given values into this formula to find the interest rate: \(r = \frac{11430 - 9000}{9000 \times 3}\)

Step 5 ：Solving the above expression gives r = 0.09

Step 6 ：Converting this decimal to a percentage gives the interest rate as 9.0%

Step 7 ：Final Answer: The loan's simple interest rate is \(\boxed{9.0\%}\)