谁能帮我解答 ..

ranth

不是很明白你的问题，有些细节也没说明。
你可以参考看看网上关于Reducing Balance Method的算法，也许可以帮到你。

Reducing Balance Method
This method is mainly used to calculate the interest payable for housing / mortgage / property loans which you can find at our home loan comparison tool and other interest payable such as overdraft (OD) facilities, and credit cards. You only pay interest on the remaining loan balance. A reducing balance interest calculation formula can be represented like this:

Interest Payable per Installment = Interest Rate per Installment * Remaining Loan Amount

参考：
https://loanstreet.com.my/learning-centre/interest-calculation-reducing-balance-flat-interest

http://www.calculatoredge.com/finance/dreducing.htm

http://www.double-entry-bookkeeping.com/depreciation/reducing-balance-depreciation-calculator/

Michael.C

哇，这些东西我真的不懂呢。。。