·       Percentage is a method of representing any quantity in fraction of 100 i.e. out of 100 how much is that quantity.
·       It is often denoted using the percent sign, "%"
·       One percent (1%) means 1 per 100 and 100% means all and so on..

Points to Remember:
·       1/5th of a number = 1/5 ×100 = 20%
·       20% of a mumber = 20/100 = 1/5th of that number.
·       If a number is increased from value A to B then % increase = (B-A)/A × 100
·       If a number is decreased from value A to B then % decrease = (A-B)/A ×100
·         If x% and y% are two successive increase(+ve) or decrease(-ve) in a number then overall  percentage of change = x + y + xy/100
·       If the population of a city increases (+ve) or decreases(-ve) by r%  every year then,
I.            Population after n year = Present Population ×(1+ r/100)n
II.        Population n years ago = Present Population ×(100/(100+r))n
·       What is the percent value A to B  = A/B × 100
Now let’s understand each of above listed point with examples one by one.

Example:
Calculate 25% of 80
 25% = 25 100

 And 25 × 80 = 20 100
So 25% of 80 is 20

Example:
A fruit seller had some apples. He sells 40% apples and still has 420 apples. Originally, he had:
Explanation:
Suppose originally he had x apples.
Then, (100 - 40)% of x = 420.
 60 x x = 420 100
 x = 420 x 100 = 700. 60
Example:
If the population of a city increases 20% every year and if its present population is 576000. What was the population of city 2 years ago.

Explanation:
This is an example of two successive change.
Population n years ago =Present Population ×(100/(100+r))n

= 576000×(100/(100+20))n

= 400000

Example:
What percentage of 5 is 3

Explanation:
=3/5×100
= 60%