The application of a certain capital (money) with compound interest.
For example:
M = C(1+i)^t
C = $ 200,00
i = 2% (0,02) per month
t = 4 months
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M = 200(1+0,02)^4
M = 200(1,02)^4
So we can say that by applying $ 200 in 4 months with an interest rate of 2% a month, we will collect that amount.