Back in school 30-odd years ago I was taught that monthly
interest on a loan/investment is the 12th root of the annual
interest, ie: loan=loan*((1+apr/100)^(1/12)).
Doing a bit of checking for some source code I find
everybody saying that monthly interest is 1/12 of the
annual interest, ie: loan=loan*((1+apr/100)/12).
Checking my mortgage statement shows my bank using
1/12 not root12. Has something changed in the last 30
years? Can banks not work out 12th roots any more, or
were my teachers wrong?
