Assists with a formula

[Rockbottom]

But the last formal does work. Notice that it does not use the .07 royalty figure.

SELL = (PROFIT% x COST + COST)/.93

I double checked it by running several sets of numbers through it, then plugging the results back into the other equations that computed your profit percentage. Which is:

PROFIT% = PROFITAR/COST

or the long way

PROFIT% = (SELL - COST - SELL x .07)/COST

I can't explain exactly why it works, because I plugged the problem equation into Wolfram Alpha for a solution, and got the .93 constant back. I suspect it takes a bit of calculus to solve the equation properly. However if you download the spreadsheet I linked, and play with it (and look at the equations) I think you will find that it works.

<img src="http://www.ipadforums.net/attachment.php?attachmentid=10513"/>

Twerppoet mentionned Wolfram Alpha. I never heard of it before and it is intriguing. I noticed there is an app but the developer web site helps in understanding what it is. Very fascinating.

Sent from my iPad2 3G 32 gig (not JB'ed) / using iPF

 

[twerppoet]

Twerppoet mentionned Wolfram Alpha. I never heard of it before and it is intriguing. I noticed there is an app but the developer web site helps in understanding what it is. Very fascinating.

Sent from my iPad2 3G 32 gig (not JB'ed) / using iPF

It's a handy site and app. I consider it one of the indispensable reference apps for the iPad. It started out geared towards math equations and terms, but has expanded into much much more. Combine it with a good dictionary/thesaurus and Wikipedia, and your iPad can substitute for a large chunk of a college library's reference section.

 

[twerppoet]

Silly question, but may I ask which apps you are all using ? I don't recognise any of the screen shots.

As Rockbottom said, most of the screen shots are from Numbers. Everything else I posted that is not Numbers, or is Numbers but with scribbling on it, was done with Skitch; a free app for scribbling on screen shots, maps, websites, and other stuff. Or, as in the case of the scrawled equations, just a blank page.

I use it a lot, and so do several other members. It's a handy (quick) way of showing things that are difficult to describe.

 

[pstar]

I would really like to see the formula that you have. The percentage shown is different then what I normally get..... ? I'm not sure how or why and trying to wrap my mind around it has cause major brain cramping!

 

[twerppoet]

Upon further reflection, I think I'm computing the % of Profit wrong. I've been calculating it as a percentage of the Cost; and after thinking about it I'm betting you are after a the % of the Sell price. Yes?

Let me go over it one more time, based on that more reasonable assumption and see what I come up with.

 

[twerppoet]

OK.

I had to fix my profit formula to show a percentage of the Sale instead of the Cost. I'm pretty sure that's where I was wrong, since the second makes a great deal more sense. It was only a minor correction; however that meant starting over with the formula to compute Sale price using Profit percentage. Experience with the first round helped, so it only took me half an hour and a dozen curse words.

Here are the new formulas. They are all enclosed in IFERROR functions to prevent accidental division by zero.

Profit% the short way.



Profit % the long way



Sell price by Profit% desired. Notice that the .93 constant appears here too.




And finally, if you want to work through it, I did the computations on paper (in pencil) this time. Feel free to ask questions, or point out where I am still wrong. Also if you find any mistakes in the Revised Profit Worksheet, let me know. I've only updated it. The first worksheet I did is the same. I'm going to say it is so I can keep it as a kind of history, but the reality is that I'm too lazy to change it right now.

Oh yes. I noticed a rounding error between tables two and three on the forth line; so there is room for improvement. It happens because I entered the rounded value in table two as input to table 3.

 

[pstar]

Anyway you can make this a download?

 

[twerppoet]

Which part? Everything there should be downloadable. The revised profit worksheet is linked. If the IPF app is giving you problems try visiting the site using Safari.

 

[Rockbottom]

From the IPF app, I had to open it in Safari and then open it in Numbers ... and then it is a full fledge Numbers editable file.

Sent from my iPad2 3G 32 gig (not JB'ed) / using iPF

 

[twerppoet]

@pstart. Did you get this to work? Or did you find someone else with better math chops? I wouldn't blame you for that.