What the heck??? The minimum monthly payment for a credit card is the larger of $5 or 1/25 of the outstanding balance. If the balance is less than $5, then the entire balance is due. If you make only the minimum payment each month, how long will it take to pay off a balance of $200? Clearly, this has to do with geometric series. I can conceptually understand this problem, but I'm having trouble putting it into mathematical terms while relating to geometric series. If you have any advice, I would greatly appreciate it. Thanks.