Financial HP Calculator: Amortisation with Payments at begin of period

[Werner]

(06-06-2024 04:05 PM)Gil Wrote:  If interests are calculated to the cent, ie with 2 digits after the comma, then if PMT1 is found equal to 2511.73389, the client should start paying — theorically—, in the armotization plan, exactly (2511.73389; 2 RND) = 2511.73.
It seems, however, that it is not what I understood from the above.

From my logic above, but I seem to be wrong?, if the growing payments show a yearly increase of 5%, then the second payment should be equal to ("exactly 2511.73" ×( 1+5/100/12); 2 RND). Or not?

I'm not sure what "exactly" it should be, but I find it more logical - and ever so slightly more accurate - to calculate the successive payments as (if payments change after a year, not every month)

PMT=2511.73389 (result of GPM solve)

then

PMT-1 = RND(PMT;2) = 2511.73
PMT-2 = RND(PMT*1.05;2) = 2637.32
PMT-3 = RND(PMT*1.05^2;2) = 2769.19
..

while here it doesn't make any difference (so far), it occasionally results in a cent more or less.. and a smaller resulting balance after amortization ;-)

Quote:Another point
Why do you use negative integer before RND command?
Is full precision not equivalent to simple 12 RND?
So that x RND, with x=0, 1, 2...11,12, should be enough to tackle all possible choices. Right?

positive numbers 0-11: the number of decimals
negative number 1-12: the number of significant digits

RND(1.23456789E-5;8)= 1.235E-5
RND(1.23456789E-5;-8)=1.2345679E-5

Cheers, Werner