This is your Investment Tool. You can purchase this Texas Instrument calculator for about $22. It may be available at Office Depot, Office Max, etc.

You will be using the following buttons.

PV = Present Value
%i = Percent Interest Return
N = Number of years
CPT = Compute
FV = Future Value

To find any of the above values, press in an amount - THEN the appropriate button.
You can enter in any order, the amount - then button. For example...

How much may a $2500 Berkshire Hathaway B be worth in 20 years at 24% return?

---> Enter 2500.
---> Enter PV.
---> Enter 20.
---> Enter N.
---> Enter 24.
---> Enter %i.
---> Enter CPT. (Always the 2nd to the last step.)
---> Enter FVto find Future Value. This amount shows up: $184,660.3745.

This is what your $2500 BRKb may be worth in 20 years!
Practice with 10 years? 30 years? 50 years? Find PV? N? %i? Have fun!