Final answer:
A retirement account that grows by a fixed amount per year would be best represented by a linear growth model, whereas growth by a percentage each year would follow an exponential growth model involving compound interest.
Step-by-step explanation:
For a retirement account that is expected to grow by a certain amount each year, the type of model that best fits this situation is called a linear growth model. This is because the account is growing by a fixed amount annually, which corresponds to a linear relationship between the time and the amount of money in the account. If we graphed this relationship, it would show a straight line, indicating consistent growth over time.
In contrast, if the account were growing by a percentage each year, this would be modeled by compound interest, which is a form of exponential growth. With compound interest, the amount of growth each year depends on the current balance of the account, resulting in a curve that gets steeper over time on a graph.