how do you work out 10%?

Ten over 100 ( ten percent ) multiply by - whatever number - over one

EG - !0% of 50

is ten over one hundred multiply by 50 over one    ( "over" denotes a fraction )

then multiply 10 by 50

and multiply 100 by one

 

__10       X       _50        =  __500     =   5

   100                  1                 100