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HP Forum Archive 15

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12c TVM
Message #1 Posted by lary on 7 Mar 2006, 2:06 a.m.

Try this example taken from Hp Journal (oct. 77) :

n=111.1111111 i=2.222222222 PV=333.3333333 PMT=4.444444444

and solve for FV

Results

HP92 : -5931.82294 (source HP Journal)

HP37E : -5931.82294

HP38E/C : -5931.82294

HP12C : -5926.306294 ???

HP10B : -5931.82294

HP17BII : -5931.82294

HP10B : -5931.82294

HP48G : -5931.82294

All but the 12C give the correct mathematical result (-5931.82294) but only the 12C gives the correct financial result(-5926.306294). In case of noninteger n, the 12c use the fractional part as a odd first period (cf hp 12c user's manual pp.50-51). With others calculators you'll have to do it yourselve (cf hp17BII owner's manual p.160).

Does anyone knows why the 12c is the only calculating with odd period ?






      
Re: 12c TVM
Message #2 Posted by Vieira, L. C. (Brazil) on 7 Mar 2006, 9:20 p.m.,
in response to message #1 by lary

Hi, Lary;

in fact, you can even control how the HP12C TVM features deal with the odd 'n' (with fractional portion different of zero).

If you press [STO][EEX] you will toggle the small C annunciator status. If the C is visible, then the fractional portion of 'n' is considered as part of the compound interest calculation. Otherwise, if the C is not visible, the fractional portion of 'n' is used seaparately, and the equivalent amount of interest due to it is computed as single interest and added to the final interest amount. In fact, as we are dealing with compound interest and a fractional period of time, the final amount of compound interest is smaller than the amount of single interest.

I am not sure if the other calculators have this sort of control.

I hope this post's contents are related to what you are asking about.

Cheers.

Luiz (Brazil)

      
Re: 12C TVM
Message #3 Posted by Karl Schneider on 10 Mar 2006, 2:36 a.m.,
in response to message #1 by lary

"Lary" --

The odd-period handling looks like a practical, real-world enhancement, designed to handle, in one step, the interest-accruing partial period after which a loan is initiated to the start date of the first regular period. The two examples of loans on pp. 59-61 (as well as my own new-car loan in the 1980's) were set up like this.

The example from the 1977 HP Journal article (JOURNALS\77OCTAC.PDF from CD #6 of the MoHPC CD-ROM set) was for the desktop HP-92, which did not have this partial-period feature. It may have been an enhancement for the HP-12C.

And why didn't the Pioneer-series financial calc's (HP-10B, HP-14B, HP-17B/17BII) retain this feature? Maybe a desire for consistency of algorithm and results between the models. Only the 17B/17BII had the built-in calendar functions (present in the HP-12C and HP-92) for calculating the number-of-days length of the partial period. Without the "delta-days" function, handling the partial period is more of a manual exercise, anyway.

PS: The "C" annunciator that Luiz talked about for this problem represents some cleverness in the Voyager platform, which included five models sharing the same display unit. C stands for "compunding" on the financial HP-12C; "complex mode" on the scientific HP-15C; and "carry bit" on the computer-science HP-16C.

-- KS

Edited: 10 Mar 2006, 2:42 a.m.

            
Re: 12C TVM
Message #4 Posted by Vieira, Luiz C. (Brazil) on 11 Mar 2006, 1:53 p.m.,
in response to message #3 by Karl Schneider

Hi, Karl;

Quote:
PS: The "C" annunciator that Luiz talked about for this problem represents some cleverness in the Voyager platform, which included five models sharing the same display unit. C stands for "compounding" on the financial HP-12C; "complex mode" on the scientific HP-15C; and "carry bit" on the computer-science HP-16C.
Indeed... From a time when designers, engineers and related 'staff' used to be composed by creative, brainy guys... and somehow users got the chance to dare facing chalenges and delve into their solutions.

I miss that.

Cheers.

Luiz (Brazil)

(PS: I do not mean that todays users do not do that, instead some of them run to their computer already running some `ready to use` SW package and let the solution come already 'packed')

Edited: 11 Mar 2006, 1:57 p.m.

      
Re: 12c TVM
Message #5 Posted by tony(nz) on 10 Mar 2006, 6:50 a.m.,
in response to message #1 by lary

I think you could get FV= -5931.822944 on the 12C by using a PV and FV adjustment of 200=4.44.../.0222... (perpetuity equivalent). First use PMT=0,PV=333.33...+200=533.33... then solve for FV and add the 200 again. n=111.11... and i=2.22... and have the "c" showing. I know you didn't want to know this<G>

Cheers, Tony

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