Which statement below is true about simple and compound interest formulas? Investments are always simple interest problems and borrowing always involves compound interest. They both assume 360 days in a year. O None of the options are true. You will use simple and compound interest formulas when you are either borrowing or investing a one-time, lump sum amount that will be repaid as a one-time, lump sum amount. The wording of the problem helps you determine if it is a simple or compound interest problem.