Question

how is calculate percentage?

Answer 1

to calculate ur percentage their is one formula
               total marks obtained*100
                     total marks
if u got 30 marks out of 50 then
30*100/50

Answer 2

it depends on which quantity X the percentage is to be calculated. Divide your quantity Q by that number X. Then multiply with 100.

     Percentage of quantity Q will be  : Q * 100 / X  =  100Q/X %

Example:

If your age is 16 and your sisters age is 10, then

  Your age is 16/10 * 100 = 160% of your sisters age
  Your sisters age is  10/16  * 100  = 62.5 % of your age