1) A supplier charges 15% interest on past-due accounts interest on $512 account is $10.52. For how many days must the account have been overdue, assuming the supplier uses a 365 day year.

2) You borrow $350 from your aunt and agree to repay her $400 in 18 months. What interest rate (to the nearest tenth) are you paying?

3) A lender makes a $4,000 90 day consumer loan interest of 10% is charged using a 360 day year. what is the APR?

4) You purchased merchandise from a supplier and failed to pay the invoice amount $310 by the last day of the credit period, Auguest 12. Calculate the total amount you must pay on October 15 if the supplier charges 18% interest on past due accounts.