How do I find out credit card balance?

Question

Thomas has a new credit card with an APR of 10.99% and a credit limit of $1800. The minimum monthly payment is 3% of the new balance. If Thomas purchases $200 in camping supplies at the beginning of the month, what will be Thomas's new balance at the end of the month? 

Express your answer rounded to the nearest cent.

Please help me figure out how to set this up.

Answer 1

Thomas has a new card and the first purchase P is for $200.00.

The card's annual interest rate i is 10.99% which is 0.1099 as a proportion.

The time period t is 1 month which is 1/12 (0.0833) of a year.

The new balance is P * (1 + i*t), which is the original balance plus interest accrued during some time period.

The new balance = $200.00 * (1 + 0.1099 * 0.0833) = $200.00 * 1.0092 = $201.84