My Math Forum  

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

Algebra Pre-Algebra and Basic Algebra Math Forum

Thanks Tree3Thanks
  • 1 Post By Greens
  • 2 Post By skipjack
LinkBack Thread Tools Display Modes
September 24th, 2019, 04:05 PM   #1
Joined: Sep 2019
From: Canada

Posts: 2
Thanks: 0

Math Focus: Algebra
Question Help with fencing question... ASAP

This question from my assignment is giving me some trouble. I feel like I'm really close but my end results still end up screwed up. If anyone can help me solve this so I can hand it in tomorrow afternoon I'd definitely appreciate it !

A farmer has 120m of fencing and plans to use it to build a rectangular garden. One side of the garden will be against his house and does not require fencing. What dimensions will allow the maximum area for this garden? What is this maximum area?
SimpleMinded is offline  
September 24th, 2019, 04:59 PM   #2
Greens's Avatar
Joined: Oct 2018
From: USA

Posts: 99
Thanks: 72

Math Focus: Algebraic Geometry
$L$ is the length of the side of the fence opposite the wall of the house, $W$ is the length of the other sides.

$L + 2W=120$

We can solve for $L$




Now we can use the vertex formula $x_v = \frac{-b}{2a}$ to find the value of $W$ where $A$ is at max.

$\frac{-b}{2a} = \frac{-120}{-4} = 30 = W$

So, we know $W=30$. We use the equation for $L$, $L=120-2W$ to find

$L=120-2(30) = 60$

So the area is at maximum when $L=60$ and $W=30$

Apply the Area formula to find the max area is

$A=60 \times 30 = 1800$
Thanks from SimpleMinded
Greens is online now  
September 24th, 2019, 08:42 PM   #3
Global Moderator
Joined: Dec 2006

Posts: 21,035
Thanks: 2271

If u and v are real and u + v is a constant, uv = ((u + v)² - (u - v)²)/4 is maximized when u = v.

For the fencing problem, let u = 120 - 2W and v = 2W, then u = v implies 120 - 2W = 2W, so W = 30, etc.
Thanks from greg1313 and SimpleMinded
skipjack is offline  

  My Math Forum > High School Math Forum > Algebra

algebra, asap, fencing, help or teach, question

Thread Tools
Display Modes

Similar Threads
Thread Thread Starter Forum Replies Last Post
Need Help ASAP kingoffightr Calculus 1 August 22nd, 2018 06:31 AM
How to solve this math question?Reply asap amni1234 Math 2 February 21st, 2016 04:07 PM
I really need help with this question ASAP urza Linear Algebra 1 October 4th, 2015 01:30 PM
Can anybody help with this question please? Due asap Hithere Algebra 2 November 21st, 2013 06:50 PM
Basic Grade 12 Calculus Multiple Choice Question Help ASAP livestrong136 Calculus 28 May 23rd, 2012 03:07 AM

Copyright © 2019 My Math Forum. All rights reserved.