Elementary Algebra

The interest formula is: i = P $\times$ r $\times$ t. To find the time needed to invest, or t, we divide i by P $\times$ r. So, t = $\frac{i}{P\ \times\ r}$ P = 4000 i = 540 r = 4.5% = 0.045 Substitute these values into the formula to obtain the time needed to invest. t = $\frac{540}{4000\times0.045}$ t = $\frac{540}{180}$ t = 3 We need to invest the amount for 3 years.