Unit 9.2 Solving for principal, rate, and time For problems in this unit, if the answer is a percent, express the answer to the nearest hundredth of a percent. 25. Explain how you could modify the simple interest formula I=PRT to get a formula designed to solve for R. For Problems 26-29, find the missing value. 26. 27. 28. 59. 30. You open a checking account. You are paid 4% interest on the average balance but are charged a $7 monthly charge. Assuming that interest is paid monthly (regardless of the number of days in the month), calculate the average daily balance you must maintain to offset the $7 monthly charge. 31. A supplier charges 15% interest on past-due accounts. Interest on an $812 account is $16.35. For how many days must the account have been overdue