way way off topic

Gary Kline kline at thought.org
Wed Oct 24 00:07:21 UTC 2012

```On Tue, Oct 23, 2012 at 08:52:49AM +0200, Polytropon wrote:
> On Tue, 23 Oct 2012 11:31:18 +0700, Olivier Nicole wrote:
> > Gary,
> >
> > On Tue, Oct 23, 2012 at 11:20 AM, Gary Kline <kline at thought.org> wrote:
> > >
> > > apologies up front for this math type quandary. I had it in a std C program,
> > > but 3+ hours of grepping havent found it.  I would have bet my last cent that I
> > > had a summary Somewhere, but cant find that either.
> > >
> > > here is the problem as best I can remember it.
> > >
> > >
> > >         let's say that john is 8 and his older friend, jim, is 22.
> > >         how much older is exact percentage terms is jim?
> >
> > That should be 22/8=2.75
> > Jim is 275% older than John
>
> Jim is 175% _older_. Why? Because 100% older means 16 years,
> as 100% refers to 8 years (8+8=16, 200% older is 8+8+8=24).
> Percentage is always a reference to something else, in this
> question, Jim's age in relation to John's. The word "older"
> means "adding percentage", refering to the base value of 8,
> "divided in 100 parts" (floating point considerations aside),
> to finally reach the value 22.
>
> If the question would be different, say, "What's the percentage
> of John's age regarding Jim's age?" In that case, it would be
> 8/22=0.3636 being 36%. Obvious: John's age is approximately
> 1/3 of Jim's age.
>
> The easiest way for creating the proper calculation is to refer
> to the equation
>
> 	                   percentage * 100
> 	percentage value = ----------------
> 	                     base value
>
> and resolve it to whatever is required.
>
> --
> Polytropon
> Magdeburg, Germany
> Happy FreeBSD user since 4.0
> Andra moi ennepe, Mousa, ...

yo; I THInk this is it. around line 4542 in my ~/.HowTo file::

%%% find percent inc/dec [increase/decrease] between two numbers.

Always figure the percentage of change relative to the original value!
For instance: * Suppose a certain item used to sell for seventy-five
cents a pound, you see that it's been marked up to eighty-one cents a
pound. What is the percent increase?

First, I have to find the absolute
increase:
Reserved 81 - 75 = 6

The price has gone up six cents. Now I can find the
percentage increase over the original price.

This percentage increase is the relative change: 6/75 = 0.08
...or an 8% increase in price per pound.

So I was wrong about ages or speed; it's the % betwen two ints;
here, the inc/dec [or change] between 75 cents as compared to
an inflated increase of 81 cents.

1.  find abs increase:  81-75 = 6;
2   find the % increase over the *original* value. 6.0/75.0
3.  percent increase using doubles is 0.08;  so a markup of six
cents is an 8% rate.

so: going back to the ages example with john bein 8, jim, 22.
22-8 is 14.
14.0/8.0 = 1.750000

175%.  jim is 175% times older than john.  which is what you found,

Or, how much more, in % is 16t than 15, it is 1.0/15.0 which is 6%.
etc,  etc.

Hm.  that's 0 for gary, 729 for polytrop!!

Ah, life:: accept no substitutes.

--
Gary Kline  kline at thought.org  http://www.thought.org  Public Service Unix
Twenty-six years of service to the Unix community.

```