(10C) Mortgage Loan Interest Rate

[Albert Chan]

Hi, Gamo

Thanks for the very good rate guess (post 4).
Rewrite in terms of C, i0 = (C - 1/C)/n

For C = nR/P = (36)(86.67)/2500 = 1.248048, i0 = 0.012411

Using my quick formula, solve for ni, thus i:

i1 = (√(12*(C - i0/2) - 3) - 3) / n = 0.012498, very good estimate

Doing interpolation with above two rates (to match C), we get i = 0.012504549

Edit: doing some plots of C vs i, discovered a even better interpolation scheme.
Interpolate to match √C instead, the line is almost straight, we get i = 0.012504546