1. Monthly payment = (loan principal ÷ repayment months)+(loan principal-accumulated amount of repaid principal) × monthly interest rate.

2. Monthly repayable principal = loan principal ÷ repayment months.

3. Monthly interest payable = residual principal × monthly interest rate = (loan principal-accumulated principal repayment amount) × monthly interest rate.

4. Decreasing monthly payment = monthly repayable principal × monthly interest rate = loan principal ÷ repayment months × monthly interest rate.

5. Total interest = [(total loan ÷ repayment months+total loan × monthly interest rate)+total loan ÷ repayment months ×( 1+ monthly interest rate)] ÷ 2× repayment months-total loan.