Hey! this is driving me crazy and I know its easy. Lets say I take out a 30 year 40,000 mortgage with interest of 11%. How do I calculate the interest and figure out the monthly payments? I thought if I did interest=principle/rate/time and multiplied it all I would get the correct answer but the answer is 381, but how do I get this answer? Can someone break this down for me step by step? I want to be able to know properly how to solve this.