Section 3: Basic Financial Functions  65 
 
File name: HP 12cpt_user's guide_English_110608.DOC  Page: 71 of 285   
Printed Date: 2009/1/13    Dimension: 14.8 cm x 21 cm 
 
The fractional part of n can be determined using either the actual number of odd 
days or the number of odd days counted on the basis of a 30-day month.
*
 The 
gÒ
 function can be used to calculate the number of odd days either way. The 
fractional part of n is a fraction of a payment period, so the number of odd days 
must be divided by the number of days in a period. If interest is compounded 
monthly, for this number you can use either 30, 365/12, or (if the odd period falls 
entirely within a single month) the actual number of days in that month. Usually, a 
monthly period is taken to be 30 days long. 
At your option, the calculations of i, PV, PMT, and FV can be performed with either 
simple interest or compound interest accruing during the odd period. If the 
C
 status 
indicator in the display is not lit, simple interest is used. To specify compound 
interest, turn the 
C
 indicator on by pressing 
?Æ
.
†
 Pressing 
?Æ
 again 
turns the 
C
 indicator off, and calculations will then be performed using simple 
interest for the odd period. 
Example 1:
 A 36-month loan for $4,500 accrues interest at a 5% annual 
percentage rate (APR), with the payments made at the end of each month. If 
interest begins accruing on this loan on February 15, 2004 (so that the first period 
begins on March 1, 2004), calculate the monthly payment, with the odd days 
counted on the basis of a 30-day month and compound interest used for the odd 
period.  
Keystrokes 
(RPN mode) 
Display  
f
CLEAR
G
    Clears financial registers. 
gÕ
 
  Sets date format to month-day-year. 
gÂ
 
  Sets payment mode to End. 
?Æ
 
 
Turns on the 
C
 indicator in the 
display, so that compound interest 
will be used for the odd period. 
2.152004
\
 
2.15 
Keys in the date interest begins 
accruing and separates it from the 
next date entered. 
3.012004 
3.012004 
Keys in the date of the beginning of 
the first period. 
 
*
 The two methods of counting odd days will yield slightly different answers. If you are 
calculating i to determine the annual percentage rate (APR) for an odd-period transaction, the 
lower APR will result if the calculation uses the greater number of odd days determined using 
the two methods. 
†
 ?Æ is not programmable.