(HP-65) Percent Functions

[Dave Britten]

Strangely, I couldn't find a program like this in the Standard Pac or any of the add-on application pacs, but this program adds the basic % and Δ% functions of other HP calculators. There was plenty of memory left over to also include versions of these functions that work directly with D.MMSS inputs.

EDIT: I've incorporated Bob's suggestion below to add a %T (percent-of-total) function to the unused E key.

Recommended Key Labels

A: %
B: Δ%
C: D.MS%
D: D.MSΔ%
E: %T

Usage

The % and D.MS% functions calculate x percent of y, and place the result in x while leaving y, z, and t unchanged (R9 is used to preserve t). The D.MS% function expects y to be in D.MMSS format, and will return the result in the same format. You can then follow these functions with + or - (or f/f^-1 D.MS+) to calculate x percent increase/decrease in y.

The Δ% and D.MSΔ% functions calculate the percent change from a starting value in y to a final value in x. D.MSΔ% expects both x and y to be in D.MMSS format. Both functions consume the values in x and y, with the result returned in x, and t being copied when the stack drops.

The %T function calculates what percentage of y is equal to x. Like the % and D.MS% functions, it leaves y, z, and t unchanged.

Code:

LBL     23
A       11
g RUp   35 09
STO     33
9       09
g RDown 35 08
EEX     43
2       02
/       81
g x><y  35 07
*       71
g LSTx  35 00
g x><y  35 07
RCL     34
9       09
g RDown 35 08
RTN     24
LBL     23
B       12
g x><y  35 07
LBL     23
1       01
-       51
g LSTx  35 00
/       81
EEX     43
2       02
*       71
RTN     24
LBL     23
C       13
g x><y  35 07
f-1     32
D.MS    03
g x><y  35 07
A       11
f       31
D.MS    03
g x><y  35 07
f       31
D.MS    03
g x><y  35 07
RTN     24
LBL     23
D       14
f-1     32
D.MS    03
g x><y  35 07
f-1     32
D.MS    03
GTO     22
1       01
LBL     23
E       15
g       35
1/x     04
A       11
g       35
1/x     04
RTN     24

[rprosperi]

Suggest adding %T, to use that lonely E key.

Since you have %, the best way is 1/X, %, 1/X, which should also preserve YZT, though I'm not 100% of stack effects of 1/X on the 65 (though I assume it too does not disturb YZT).

[Dave Britten]

(01-11-2020 06:45 PM)rprosperi Wrote:  Suggest adding %T, to use that lonely E key.

Since you have %, the best way is 1/X, %, 1/X, which should also preserve YZT, though I'm not 100% of stack effects of 1/X on the 65 (though I assume it too does not disturb YZT).

Oh yeah, that's a good idea. I was trying to come up with something to put on E and use a bit more of the available memory.

[Paul Dale]

I've never used %D.MS. What disciplines use it and what for?

The 34S includes these other percentage functions:

Percent margin:
\[ \%MG = 100 \cdot \frac{x-y}{x} \]

Sales price (add a margin of x% to the cost y):
\[ \%+MG = \frac{y}{1-\frac{x}{100}} \]

Mean rate of return as a percentage:
\[ \%MRR = 100 \left( \sqrt[z]{\frac xy} - 1 \right) \]

Pauli

[Gamo]

Even more strange is that HP-65/67/97 Standard Pac or Business Pac doesn't

have the Business Percent on Pricing Calaculations or I called the Profit on Pricing.

HP 10BII got this Pricing function with Cost, Price, Markup and Margin where

user enter two known data and calculator find the answer of the remaining two answer.

I did try to program this function on HP-67 and here is the link

https://www.hpmuseum.org/forum/thread-12987.html

I also adapted this to work on the HP-41C too.

https://www.hpmuseum.org/forum/thread-14258.html

This program also work if user need to calculate [TAX-] and [TAX+]
simply by entering the tax rate at [C]
Enter Price including Tax on [B] and find Price without Tax on [A]


Gamo

[Dave Britten]

(01-12-2020 03:59 AM)Paul Dale Wrote:  I've never used %D.MS. What disciplines use it and what for?

I think it's more likely it would be used for intervals of time rather than angle measurements.

Margin and markup would probably be best suited to a separate card so there would (hopefully) be enough room and keys to implement solve-for-any-variable (cost, price, margin, markup).

[SlideRule]

(01-12-2020 03:59 AM)Paul Dale Wrote:  I've never used %D.MS. What disciplines use it and what for?

Surveying? try Convert Slope Percent (%, Slope (grade) Units) to Degrees, Minutes, Seconds (d°m′s″, Common Units)

Example: 7% slope (steep roadway incline) ≈ 4º 0' 15.02"

BEST!
SlideRule

[Dave Britten]

(01-12-2020 02:52 PM)SlideRule Wrote:  

(01-12-2020 03:59 AM)Paul Dale Wrote:  I've never used %D.MS. What disciplines use it and what for?

Surveying? try Convert Slope Percent (%, Slope (grade) Units) to Degrees, Minutes, Seconds (d°m′s″, Common Units)

Example: 7% slope (steep roadway incline) ≈ 4º 0' 15.02"

BEST!
SlideRule

Looks like that's a slightly different calculation: arctan(x/100) where x is the slope percent. I haven't looked through the Survey Pac much, but I'll bet there's a card in there for converting between grades and degrees.

EDIT: Nope, looks like they didn't bother including it as a separate card, because it's such a simple calculation.