Math Formulae: Percentages

 Here are some important formulae related to Percentages

1. Fraction to percentage: Multiply fraction by 100 and put % sign.
   
   
2. Percentage to Fraction: Divide percentage by 100, reduce fraction to simplest form and remove % sign.
   
   
3. Decimal to percentage: Move decimal point 2 places to the right and add % sign.
   
   
4. Percentage to Decimal: Move decimal point 2 places to the left and remove % sign.
   
   
5. Fraction-Percentage values to remember:
   

   	1
   	2

      =  50 %, 

   	1
   	3

      =  33.33 %, 

   	1
   	4

      =  25 %,
   
   

   	1
   	5

      =  20 %, 

   	1
   	6

      =  16.66 %, 

   	1
   	7

      =  14.28 %,
   
   

   	1
   	8

      =  12.25 %, 

   	1
   	9

      =  11.11 %, 

   	1
   	10

      =  10 %,
   
   

   	1
   	11

      =  9.09 %, 

   	1
   	12

      =  8.33 %, 

   	1
   	13

      =  7.69 %,
   
   

   	1
   	14

      =  7.14 %, 

   	1
   	15

      =  6.66 %, 

   	1
   	16

      =  6.25 %,
   
   

   	1
   	17

      =  5.88 %, 

   	1
   	18

      =  5.55 %, 

   	1
   	19

      =  5.25 %,
   
   

   	1
   	20

      =  5 %, 

   	1
   	25

      =  4 %, 

   	1
   	50

      =  2 %,
   
   Examples:
   1. 6.25 % of 320 = 

   	320
   	16

      =  20
   
   2. 20 % of 630 = 

   	630
   	5

      =  126
   
   
6. Quantity X as percentage of quantity Y = 

   	X
   	Y

    × 100
   
   
7. What percentage of a is b = 

   	b
   	a

    × 100
   
   
8. Percentage increase or decrease in a quantity = 

   	Actual increase/decrease
   	Original quantity

    × 100
   
   
9. What percentage is X more than Y = 

   	(X - Y)
   	Y

    × 100
   
   
10. What percentage is X less than Y = 

    	(Y - X)
    	Y

     × 100

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