Я не думаю, что это всего лишь одно уравнение или формула, с помощью которой вы можете найти совокупный процент, выплачиваемый между двумя периодами. Это то, что вы должны сделать
a) Find the monthly payment keeping in view whether the payment is made at the end or at the beginning of period [PMT]
b) Find the total interest paid by the end period
1. Find the outstanding principal by the end period [OP_E]
2. Find the total principal paid by the end period [TP_E] = PV - [OP_E]
3. Find the total amount paid by the end period [TA_E] = PMT x end
4. Find the total interest paid by the end period [TI_E] = [TA_E] - [TP_E]
c) Find the total interest paid by the start period minus 1
1. Find the outstanding principal by the start period [OP_S-1]
2. Find the total principal paid by the start period [TP_S-1] = PV - [OP_S-1]
3. Find the total amount paid by the start period [TA_S-1] = PMT x start - 1
4. Find the total interest paid by the start period [TI_S-1] = [TA_S-1] - [TP_S-1]
d) Now find the CUMIPMT = [TI_E] - [TI_S-1]
Этот Калькулятор CUMIPMT использует вышеуказанный или аналогичный алгоритм для расчета совокупного процента , выплаченного по кредиту