Anu wrote: "We use the decimal system because there are ten fingers on our hands."
This might be one of the reasons. However, there are mathematical reasons that made people use it: The decimal system is much more practical than the hexagesimal system the Babylonians used or the duodecimal one. At least for human beings - computers are much more comfortable with either the binary system or the ...dunno... 0-to-F system (FF being 255 in "real numbers" ;-)
We can add, multiply... numbers in a most elegant and easy way using the decimal system, much easier than in any other system. Try and calculate 7% of 20 Euros or Dollars using the decimal system and then do the same using the decimal system or the binary system :-)
However, considering the poor performance of way too many young people when it comes to most basic calculations as the one mentioned above none of the system seems to be working. How come? :confused: