Math Formulae: Interest

Here are some interest related formulae that can be handy in exam time:

Terms Used: SI = Simple Interest,    CI = Compound Interest,    , A = Amount

P = Principle,    t = Time,    r = rate of interest,    I = Interest

• A = P + I
  
  
• Simple Interest:
  
  1. SI = 

     	P × r × t
     	100

     
     
     
  2. A = P + 

     	P × r × t
     	100

        =  P 

     ( 1 +	r.t	)
     	100

     
     
     
• Compound Interest:
  
  1. CI = A - P
     
     
  2. A = P 

     ( 1 +	r	)	t
     	100

        , when interest rates are compounded yearly.
     
     
  3. A = P 

     ( 1 +	r/2	)	2t
     	100

        , when interest rates are compounded half-yearly.
     
     
  4. A = P 

     ( 1 +	r/4	)	4t
     	100

        , when interest rates are compounded quarterly.
     
     
• For first year, CI = SI
  
  
• For two years,
     CI - SI = P 

  (	r	)	²
  	100

  
  
  
• For three years,
     CI - SI = P 

  (	r	)	²
  	100

   

  (	r	+ 3	)
  	100

  
  
  
• Population: Total population (P) after t years,
     when population rises, P = P_i 

  (	1 +	r	)	t
  		100

  
     and, when it declines, P = P_i 

  (	1 -	r	)	t
  		100

  
  where P_i is initial population of area, and r is rate of increase or decrease of population.
  
  
• Depriciation: Depriciation in value of a product after t years,
      V_f = V_i 

  (	1 -	r	)	t
  		100

  
  where, V_f is final value of product,
  V_i is initial value, and
  r is rate of depreciation in value of product.

These formulae can be found in formula book under tools section of Tricky Maths App.