Joanne has taken out a €200,000 mortgage over 20 years at 8% per annum. Calculate her repayment amount per annum to amortize the mortgage.
We apply the formula to calculate her annual repayment:
A=\frac{P\;r}{\left[1-\frac{1}{(1+r)^{n}}\right]}A=\frac{200000\ \ast\ 0.08}{\left[1-\frac{1}{(1+0.08)^{20}}\right]}
= \frac{160000}{\left[1-\frac{1}{4.661}\right]}
= €20,370
We adjust the formula for the more common case where the interest is compounded several times per year (usually monthly), and so n = # years ∗ # compoundings, and the interest rate per compounding period is i = r/# compoundings.