My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Reply
 
LinkBack Thread Tools Display Modes
October 12th, 2011, 05:08 PM   #1
Newbie
 
Joined: Sep 2011

Posts: 13
Thanks: 0

mathematical modeling

a farmer needs to build a rectangular pen next to his driveway. its area must be 600 square meters. the fence for the driveway side of the pen costs 5 dollars per meter, and the fence for the other three sides costs only 3 dollars per meter.

find a function that models the cost of the fence in terms of the length of the driveway side in terms of the length of the driveway.

is this right? 3(3x)+5y= cost

xy=600 so x=600/y the would you plug this in for x?
hannah2329 is offline  
 
October 12th, 2011, 05:52 PM   #2
Senior Member
 
MarkFL's Avatar
 
Joined: Jul 2010
From: St. Augustine, FL., U.S.A.'s oldest city

Posts: 12,211
Thanks: 521

Math Focus: Calculus/ODEs
Re: mathematical modeling

Letting y be the length of fence along the driveway, and x be the perpendicular length of the rectangle, we find the cost C in dollars:

C = 5y + 3(2x + y) = 8y + 6x

We know xy = 600, thus x = 600/y, then:

C(y) = 8y+6(600/y) = 8(y + 450/y)

You were on the right track, you just made the 3 $3/m sides equal to x in length, when 2 of them are x and 1 is y, the side opposite the one next to the driveway. Make a sketch and you will clearly see what I am talking about.
MarkFL is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
mathematical, modeling



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Mathematical modeling hannah2329 Algebra 1 January 6th, 2012 08:18 AM
Modeling clandarkfire Calculus 1 November 15th, 2011 12:52 PM
mathematical modeling hannah2329 Algebra 1 October 11th, 2011 10:11 AM
Mathematical modeling hannah2329 Algebra 1 October 11th, 2011 10:09 AM
Mathematical modeling - a task psihomehanicar Algebra 1 December 2nd, 2010 10:56 AM





Copyright © 2019 My Math Forum. All rights reserved.