20070201
7-3-1
Compound Interest
   
PV  : present value
   
FV  : future value
   
PMT  : payment
   n   :  number of compound periods
   
I  %   :  annual interest rate
  
   i  is calculated using Newton’s Method.
  
   S  = 0 assumed for end of term 
   
S  = 1 assumed for beginning of term 
  
  
  
  
  
  
  
  
  
  
  
  
   F ( i ) = Formula  I 
  
  
  
  
  
  
  
  u  Formula  II  ( I  % = 0)
  
  
  
  Here:
  
  
i(1 +  i)
n
 (1 + i ×
 
S)[(1 +  i)
n
 –1]
=
α
i(1 +  i)
n
 (1 + i ×
 
S)[(1 +  i)
n
 –1]
=
α
(1+ i)
n
 1
=
β
(1+ i)
n
 1
=
β
+ (1 + i × S)[n(1 + i)
–n–1
]+
 
–
 nFV(1 + i)
–n–1
ii
PMT
 (1 + i × S)[1 – (1 + i)
–n
]
F(i)' =  –
[
+S [1 – (1 + i)
–n
]
]
+ (1 + i × S)[n(1 + i)
–n–1
]+
 
–
 nFV(1 + i)
–n–1
ii
PMT
 (1 + i × S)[1 – (1 + i)
–n
]
F(i)' =  –
[
+S [1 – (1 + i)
–n
]
]
PV + PMT × n + FV = 0 PV + PMT × n + FV = 0 
PV = – (PMT × n + FV )PV = – (PMT × n + FV )
  7-3  Compound Interest
  This calculator uses the following standard formulas to calculate compound interest.
  u  Formula  I 
  
  
  
  Here:
  
  
  
  
  
  
  
  
  
  
  
  
  
  
PV + PMT × + FV
i(1 + i)
n
(1 + i)
n
 (1 + i × S)[(1+ i)
n
 –1] 1
 = 0
i = 
100
I %
PV + PMT × + FV
i(1 + i)
n
(1 + i)
n
 (1 + i × S)[(1+ i)
n
 –1] 1
 = 0
i = 
100
I %
PV = –(PMT ×
 
 + FV × 
 
)
 
β
α
PV = –(PMT ×
 
 + FV × 
 
)
 
β
α
FV = –  
β
 PMT ×
 
  + PV
α
FV = –  
β
 PMT ×
 
  + PV
α
PMT  = – 
β
 PV + FV ×
α
PMT  = – 
β
 PV + FV ×
α
n = 
log
{                                    }
 log(1 + i)
 (1+ i × S ) PMT + PVi
 (1+ i × S ) PMT – FVi
n = 
log
{                                    }
 log(1 + i)
 (1+ i × S ) PMT + PVi
 (1+ i × S ) PMT – FVi