"n" function in HP 12C

[Luc]

Hi all,
Any one know why the HP 12C calculator rounds the calculated value of "n" up to the next higher integer?

Example: for a financial problem, when we solve to get the Number of Payments or Compounding Periods "n", the correct answer is n=3.1 years (just for example), but the HP 12c will answer n=4 years.

Oh, It's surprised.

And, this situation also occur on the Financial Consultant Casio FC-200.

Luc

[Gene]

Well, in truth, you can't make 3.1 payments in real life. The designers decided that they would report a value for n that would make sure the PV or FV had actually been reached.

In your example, after 3 payments, you haven't quite had enough put in. At 4 payments, you are beyond it. They chose to use 4 rather than 3, and didn't like the "exact" solution for n as noted above.

That said, I wish they had decided to just report the real n and let users round up. Users are not stupid, but that's something calculator designers sometimes forget.

Cheers!

[Luc]

Hi Gene, Are you "Gene Wright" author of some books in which is "Quantitative Analysis For Business - The Time Value of Money and Basic Business Statistics - Using a Business Calculator"book ? I saw on Amazon, but the book is expensive (as for me - Vietnamese) > 40USD.

OK, thank you for you answer !!!

But in HP 10B, it is not happen that case of "n", HP 10B give a correct answer, it same to answer og TI BAII+.

And HP 12C and Casio FC-200 gave an answer of "n" same together with round up to next interger.

cheers
Luc

Edited: 1 Aug 2003, 9:06 p.m.

[Gene]

Yep, that's me. Sorry for the high price. I can't do a very big print run and that drives unit cost up. :-(

They implemented the solution for n differently in the HP-10B, etc. I dont' know why the HP-12c was made the way it was.

The BAII Plus is a great cheap calculator for business students. If they made a good keyboard it would be fantastic. Our university changed the recommended calculator to the TI BAII Plus last year because of the terrible HP-10BII keyboard.

Sadly, leaked pics of the new business calculators rumored to be coming appear to show the same keyboard. I hope they worked that part out.

[hugh]

also, the 12c has a special meaning for n input as a non-integer. the fractional part is intended for the odd payment. ie that fractional part of loans to cover the intermediate time before it starts proper.

only as input tho'.