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4.0  INTEREST FROM ANNUITY AND COMPOUNDING
It is not necessary to be a mathematician to calulate annuities or compound interests.
There are websites to perform these calcualtions for you.
4.1  COMPOUND INTEREST

The initial amount of money, aka as initial principal (denoted by the symbol, Po) appreciates
to a Total amount (denoted by the symbol P) based on the compounding at an average interest
rate (denoted by the symbol i or r) and the frequency of the compounding which is usually in
years (denoted by n).  Mathematically this is expressed by the following formula:




By using the website at: http://www.1728.org/compint.htm
specifying any 3 of the 4 parameters, the site will calculate the 4th parameter.

4.2  ANNUITY

​An annuity differs from compound interest in that an initial (fixed) amount is not used for compounding.
Instead, an amount is added each period (such as monthly or yearly) at a fixed interest rate for a period
of time to reach a total value of the annuity.  Mathematically this is expressed by the following formula





                      where:"r" is the annual rate of return
                       and   "n" is the number of years

by using the website at: http://www.1728.org/annuity.htm 
specifying any 3 of the 4 parameters, the site will calculate the 4th parameter.