Divide the APR by 360 days and multiply it by 30 days to get the monthly interest. Each loan is usually secured by the car you bought. So we will use the secured APR.

8. Average rating secured apr: 5.85% divide by 360 multiply by 30: 0.4875% monthly rate

Cost of car: 19,725 ; sales tax: 4.75% ; down payment: 2,175

19,725 x 1.0475 = 20,661.94 - 2,175 = 18,486.94 loan amount

18,486.94 x 0.4875% = 90.12 accrued interest for the 1st month.

9. Excellent rating secured apr: 4.80% divide by 360 multiply by 30: 0.40% monthly rate

Cost of car: 15,867 ; sales tax: 5.25% ; down payment: 10% of total cost

15,867 x 1.0525 = 16,700.02 x 90% = 15,030.02 the principal balance at the start of the loan.

10. Fair rating secured apr: 7% divide by 360 multiply by 30: 0.5833% monthly rate

Cost of new car: 19,072 ; sales tax: 4.5% ; down payment: 1,200

Cost of used car: 15,365; sales tax: 4.5% ; down payment: 1,200

19,072 x 1.045 = 19,930.24 - 1,200 = 18,730.24

18,730.24 x 0.5833% = 109.25 accrued interest

15,365 x 1.045 = 16,056.43 - 1,200 = 14,856.43

14,856.43 x 0.5833% = 86.66 accrued interest

109.25 - 86.66 = 22.59 is the difference in interest accrued by the end of the first month.