Question 175070
These formulas are cumbersome to calculate on paper. You would be better served
if you use a calc like a Ti83, financial application. With this you can enter
and combination of interest rate, loan amt, no. of payments, payment amt and 
immediately determine what you want to know.
:
For instance if you have loan of 415,000 with an interest rate of 5%, and the
monthly payment has to be 2362, enter these values and and find the number
 payments required to pay it off. About 317 payments or about 26 yrs. Or any
 other combination of interest, payment amt, time, etc can be easily determined.
:
With practice you can find out anything you want about a mortgage in minutes