I suck at mathematics...

Kashluk · Post by **Kashluk** » Thu Jan 20, 2005 4:28 pm

... therefore I need your help. This isn't a home assignment or anything, it's just something that's been puzzling me about functions / derivatas etc. I'm on my second course of this specific matter but I still can't draw profitability figures!

The problem is as follows:

Research has shown that if the shop owner lowers the price of his merchandise by p %, their sales will grow by 1,1p %. Optimize the shop owner's sales strategy (ie. With what value of p can he earn the most?)

I know that I can find the peaks and lows from the zero points when I derive the function, but I'm having trouble making the function in the first place. I mean, how could it be done as simply as possible? It's simpler with just one factor, but I think calculating this out requires two? And as I said, I can handle it from the f'(x) point onward, I just need to get to the f(x) phase first...

Yes, I know. I suck at maths.

Nicolai · Post by **Nicolai** » Thu Jan 20, 2005 4:33 pm

Here's my suggestion.

Blargh · Post by **Blargh** » Thu Jan 20, 2005 4:35 pm

Now, I consider myself to be at least somewhat intelligent. Yet maths of anything other than the simplest varieties makes my eyes burn with the bitter tears of frustration, metaphorically writing. Extremely irritating that.

Ozrat · Post by **Ozrat** » Thu Jan 20, 2005 8:52 pm

Is this economics math, calculus-related, probability, statistics.... what? Elaborate please, if this is your second course in this math field.

Spazmo · Post by **Spazmo** » Thu Jan 20, 2005 9:07 pm

Your only variable is p (the percentage by which you drop the price, probably smarter to express it in straight up decimal), so don't sweat multivar shit. P = profit = # sales * price . # sales = m * (1.1p + 1) where m is the base number of sales and constant. price = (n * [1-p]) where n is the base price and a constant.

So I think the total function is P = (m * [1.1p + 1]) * (n * [1-p])

And so P = (1.1pm + m) * (n - np)

= 1.1pmn - 1.1p^2mn + mn - pmn

=0.1pmn + (1 - 1.1p^2)mn

= (0.1p + 1 - 1.1p^2)mn

m and n are constant as stated above:

m = base number of sales
n = base price
p = price drop in percentage (remember that 25% = 0.25 and so on when fitting p into the function)

And it's a cute lil upside down parabola.

I think.

And word to the wise, writing decimals with a comma is for Eurocommies, real men use decimal POINTS.

Kashluk · Post by **Kashluk** » Thu Jan 20, 2005 9:08 pm

Well, the schooling system over here in Finland differs quite a lot from the one you have in Canada, but to make a long story short: I'm on "senior high school" at the moment and I get to choose between two lines of mathematics. The short route or the long route, while the short route doesn't get any more complicated from (ax^2+bx+c) the long route prepares us for university math, some of the latter courses actually being almost identical to first uni-level courses.

Long route means 10 courses (short's only 6), which is in other words 60 weeks of study, 4 lessons a week. I'm on the 7th at the moment. The 6th and 7th course have concentrated on deriving functions and all practical forms of it. So I was browsing through my book, frustrated because I couldn't find anything that was even close to real world (I mean, fucking around with some symmetrical figures and meaningless numbers gets kind of idiotic after a while), when I stumbled upon that puzzle/job/whatever I described in my first post.

And so I took it as my mini-crusade to solve it, no matter what. I hope you're happy with my explination and can start helping me out now, engie

EDIT: Ok, yo yo, Spazmo answered while I was typing to Ozie. Stay tuned for my response.

MurPHy · Post by **MurPHy** » Thu Jan 20, 2005 9:15 pm

Spazmo wrote:And word to the wise, writing decimals with a comma is for Eurocommies, real men use decimal POINTS.

The funny thing is I saw a comma used instead of a decimal point on a box of South African 7.62mm NATO ammo I bought a while back (it was stated as "7,62 NATO").

Kashluk · Post by **Kashluk** » Thu Jan 20, 2005 9:31 pm

Alrighty, Spazmo.

I turned around the function a little bit so it's more familiar to me, I hope you won't mind?
The commas are still there, too - for the proletariat! Anyways, let's hit it:

So, dealing with
f(x) = (0,1p + 1 - 1,1p^2)mn
requires derivation:

f'(x) = (0,1 + 0 - 2*[1,1p]) + 0
= - 2,2p + 0,1 = 0

The above equals nil, because the peak can be found from the point where the derivat changes direction, right?

2,2p = 0,1
p = 0,0454...
0,0454*100 ~ 4,5 % !

And according to the back pages of my book... It's correct. Thank you very much, Spaz.
You've lifted a rock off of my heart. Now I can finally sleep my nights well.

XXX OOO

Your dearest friend at the moment,
Senior Captain Kashluk Buttlugian (jr)

Mandalorian FaLLouT GoD · Thu Jan 20, 2005 9:35 pm

Why is it that math on the internet looks retarded and takes 60 more steps than required?

Spazmo · Post by **Spazmo** » Thu Jan 20, 2005 9:36 pm

Always happy to wave my math penis around. Not such a difficult problem, of course.

Kashluk · Post by **Kashluk** » Thu Jan 20, 2005 9:40 pm

Well, I was pretty close to what you posted (the early parts of your post, to be more accurate) when I decided to give up. I was trying to do it the way-too-difficult-way though, with multible variables and shit. "Simplicity is the answer"? I dunno. But thanks anyways, you learn something new every day.

Radoteur · Post by **Radoteur** » Mon Jan 24, 2005 1:47 pm

Don't feel bad. I failed math 124: Differential calculus.

I'm taking it again.
Mainly because I didn't do the homework and just played video games and jerked off.

Lynxer · Post by **Lynxer** » Mon Jan 24, 2005 2:54 pm

I always wondered how people can concentrate on mathematics.......it's so utterly BORING.

the guardian · Post by **the guardian** » Mon Jan 24, 2005 3:45 pm

If memory serves me right you wrote that you're studying medical biology, Lynxer. While I like the subject myself, I'm sure I don't have to tell you that most people regard it as "utterly BORING", as you put it.

POOPERSCOOPER · Post by **POOPERSCOOPER** » Tue Jan 25, 2005 1:45 am

I like math mainly because I freakin suck at English. I dont know how to elaborate or write good. You dont have to think in math, it just all procedures unless you have to use it in real life then your screwed.

Subhuman · Post by **Subhuman** » Tue Jan 25, 2005 2:06 am

I'm the opposite. Math is boring as fuck because you can't do anything with it. English is a breeze; just think up a bunch of meaningless, pretentious wankdoodle, call it a term paper, and you've got an A.

Spazmo · Post by **Spazmo** » Tue Jan 25, 2005 2:17 am

Comparing the intrinsic value of math versus language is totally masturbatory since they're both essential to the development of civilization.

That said, I'm sure Subhuman can't do anything with math because he's a total muffinhead. For real (wo)men, math is one of the most rewarding things to study because it gets pretty fucking cool once you really get in there.

Subhuman · Post by **Subhuman** » Tue Jan 25, 2005 3:39 am

If by "cool" you mean "mind-numbingly repetitive, tedious and boring", then yeah, math is hella cool.

Post by **King of Creation** » Tue Jan 25, 2005 3:42 am

This is why I'm majoring in nothing mathematicall.

Blargh · Post by **Blargh** » Tue Jan 25, 2005 3:56 am

As I've seen the gleam of mathematical ecstasy in the eyes of students, friends and colleagues, I know it must be wildly intriguing to some, I also know that I will probably never experience it on that level. I'll cope though, as I frequently experience a fantastic purely intellectual high from writing and sharing that work and the resultant camaraderie and debate with others of similar interests. Huzzah.