College Algebra (10th Edition)

The amount A after t years due to a principal P invested at an annual interest rate r, expressed as a decimal, compounded n times per year is $A=P\displaystyle \cdot(1+\frac{r}{n})^{nt}$ If compounding is continuous, $A=Pe^{rt}$ --- Will: $A=2000\displaystyle \left(1+\frac{0.09}{2}\right)^{(2)(20)}={{\$}} 11,632.73$Henry:$A=2000e^{(0.085)(20)}={{\$}} 10,947.89$ After 20 years, Will has more than Henry.