Percentage

Percentage means a rate, number or amount in each hundred.

x percentage is written as x% and expressed as x/100.

Hence, ( a/b ) is expressed as percentage = ( a/b * 100 )

Example :

20 % =  ( 20/100 ) = ( 2/10 ) = ( 1/5)

1.25 % = ( 1.25/100 ) = ( 125 / ( 100 * 100 ) ) = ( 5 / ( 4 * 100 )) = ( 1/100 ) = 0.01

Some facts:

(1) Population Calculations:

Let the population of a town is P and it increases at the rate of R % per annum then,
Population after n years = P * ( 1 + ( R/100) )ⁿ
Population n years ago = P / ( 1 + ( R/100) )ⁿ

(2) Depreciation of a product:

Let the present value of a product is P and it depreciates at the rate of R % per annum then,
Value of the product after n years =  P * ( 1 - ( R/100) )ⁿ
Value of the product n years ago = P / ( 1 - ( R/100) )ⁿ