VAT calculations with RPN-calculator - Printable Version +- HP Forums (https://archived.hpcalc.org/museumforum) +-- Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum-1.html) +--- Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum-2.html) +--- Thread: VAT calculations with RPN-calculator (/thread-83128.html) VAT calculations with RPN-calculator - Kalevipoeg - 11-26-2005 I like to tell you how I became more familiar with % function of the HP12c. VAT = Value Added Tax (in the European Union) ```NET = GROSS/(1+(VAT RATE/100)) VAT = NET*(VAT RATE/100) ``` I wanted to write a short program which a) calculates NET amount into Y register and b) calculates VAT into X register. In this case VAT RATE is stored in R0-register. Usage: Key in the GROSS amount and press [R/S]. First I wrote the following program (16 steps) ```01 RCL 0 02 1 03 0 04 0 05 / 06 1 07 + 08 / 09 ENTER 10 ENTER 11 RCL 0 12 1 13 0 14 0 15 / 16 * ``` Then I realized my calculator has a % function and I wrote my program again (now 7 steps) ```01 1 02 RCL 0 03 % 04 + 05 / 06 RCL 0 07 % ``` The % function of the RPN-calculators is more useful function than I believed! % vs. delta-% - Karl Schneider - 11-27-2005 Kalevipoeg -- Good thinking! Of course, "per cent" means "per 100", so those are logical simplifications. Among Voyagers, only the HP-12C and HP-10C have a "%" key as an unshifted function. I believe that "%" is much more useful in business than in science and engineering, in which "delta-%" is more useful. It makes sense to me that the 12C would have "%" unshifted. However, the basic scientific 10C omitted "delta-%", while providing "%" unshifted. Not good thinking... Re: VAT calculations with RPN-calculator - tony (nz) - 11-28-2005 Hello Kalevipoeg. Nice to see you again. Today I learned from Wikipedia that you must be the son of Kalev :-) Indeed it can be very handy the way % preserves Y. I once had fun using i,PV and FV (with n=1 and PMT=0) to do all shopkeeper markup/markdown calculations, which parallel VAT/normal_tax(eg income tax) calculations. The markdown and income tax percentages need to be entered as negative. It takes a bit of getting used to as PV and FV have opposite signs, but we usually know which is the larger. And then PV+FV gives the amount of the tax for example. Yes, I remember now, last year in Datafile V23N2P14/15, I wrote about this - also showing how to calculate markup given markdown, and vice-versa. So you could set FV=GROSS, i=VAT RATE. Then solving for PV gives -NET. You can input any two, and solve for the third - not that this is very useful, except if you are a tax consultant or a shopkeeper :-) But it is fun to try and do many calculations, actually seen in daily life, with one equation: PV*(1+i/100)+FV=0. BTW I have submitted some 12C games to HPCC Datafile and I mention your name in bold when presenting lunar lander, referring folk to your Moon Landing Simulator as published here early last month. I hope you don't mind - I never thought to ask! Cheers, Tony Re: VAT calculations with RPN-calculator - Kalevipoeg - 11-28-2005 Thank you Tony. I'm happy you mentioned my name. Thanks. About VAT calculations Why did I want to calculate NET amount into Y register and VAT into X register? Answer: Now I can use Sigma+ to calculate totals if necessary. Edited: 28 Nov 2005, 7:41 a.m.