$67500.00 dollars is invested at 3.4% using simple interest. If the future value is $115695.00, how long was it invested? Round to the nearest tenth of a year.

Using $LaTeX: \displaystyle FV = PV +PVrt \iff FV - PV = PVrt \iff t = \frac{FV - PV}{PVr}$ . Evaluating gives $LaTeX: \displaystyle t = \frac{115695.0-67500}{(67500)(0.034)} = 21.0$ years