To earn $500 in interest at a 4% annual rate, you need to leave $2000 in the account for approximately 6.25 years.
The formula for simple interest is given by:
![\[ I = P * r * t \]](https://img.qammunity.org/2018/formulas/mathematics/high-school/f8zqhdtyi8l6zwyigtwzw4czy4x4kwxwxd.png)
Where:
- I is the interest earned,
- P is the principal amount (initial deposit),
- r is the annual interest rate (expressed as a decimal), and
- t is the time the money is invested or borrowed in years.
In this case, you want to find t, so rearrange the formula to solve for t:
![\[ t = (I)/(P * r) \]](https://img.qammunity.org/2018/formulas/mathematics/high-school/stseyi0dvbrbjk1ol3v79voy667yf17j31.png)
Given that P = $2000, r = 0.04 (4% as a decimal), and I = $500, plug these values into the formula:
![\[ t = (500)/(2000 * 0.04) \]](https://img.qammunity.org/2018/formulas/mathematics/high-school/zaicougtwbqo455byz6bosldbz414iuy3b.png)
Calculate the result to find out how long you must leave the money in the account to earn $500 in interest.
![\[ t = (500)/(2000 * 0.04) \]\[ t = (500)/(80) \]\[ t = 6.25 \]](https://img.qammunity.org/2018/formulas/mathematics/high-school/o2oktpl7zb22v5xo3l2evco1trwrd036py.png)
Therefore, you must leave the money in the account for approximately 6.25 years to earn $500 in interest at a simple annual rate of 4%.