Model the situation using a differential equation. State the units of each variable and the units of the derivative.
Every month Donna's savings account earns 2 percent interest and she deposits an additional $100 dollars.
Let S be the amount of money in Donna's account and t be time in months. Every month Donna's account gains 2 percent or .02S in interest, and also gains $100. therefore the rate at which her savings account grows is
Since no money is taken out in this problem, we don't need to worry about the rate at which money leaves.