wikiHow Calculating Interest Rate Answers 1. Total interest charged: $1,800. 2. Total amount owed: $7,446.58. 3. Yield to maturity: 5.26%. 4. Interest earned in one year: $20. 5. Interest charged for one month: $30. 6. Monthly payment: $361.35. 7. Total amount earned: $4,010.38. 8. Total interest charged: $1,478.63. 9. Monthly payment: $1,193.54. 10. Present value of annuity: $47,042.45. 11. Total amount owed: $64,586.15. 12. Yield to maturity: 4.77%. 13. Monthly payment: $212.09. 14. Total amount earned: $122.99. 15. Interest earned in 5 years: $202.71. Page