Equal principal and interest method: suppose the annual interest rate was 4.900% and the total loan was 690,000. The loan term is 30 years: the monthly repayment of principal and interest is 3662.0 1 yuan, the total repayment is 13 18323.6 yuan, and the total interest payable is 628,323.6 yuan. The interest paid in the first month is 28 17.5, and the principal paid in the first month is 844.5438+0; The interest paid in the second month is 28 14.05, and the principal paid in the second month is 847.96; Since then, the monthly interest repayment amount has decreased and the principal has increased. (without considering the adjustment of interest rate in the middle)