# Math Help - Shortest fence distance

1. ## Shortest fence distance

Hi All,

Code:
A rancher wants to fence in an area of 2000000
square feet in a rectangular field and then
divide it in half with a fence down the middle
parallel to one side. What is the shortest
length of fence that the rancher can use?
My Work..

Code:
2000000 = ab ---> b = 2000000/a

L = 3a + 2b = 3a + 4000000/a

0 = L' = 3 - 4000000 / a^2

a = 3651.48ft

b = 4000000/ 3651.48 = 1095.45ft

Lmin = 3(3651.48) + 2(1095.45) =!?  13145.3ft

Any help is appreciated! I was following along with this example:
http://www.mathhelpforum.com/math-he...n-problem.html

-M

2. you put an extra zero in your calculator when you find out a.

recalculate a and its good

3. Haytham, Thanks for looking..

I did what you said and got 10392.3 for Lmin. However the program I am using is telling me it's the wrong answer. Could you or someone else confirm this?

Thank you,

-M

4. sorry didnt notice

b=2000000/a

you used b=4000000/a

5. Originally Posted by mant1s
Haytham, Thanks for looking..

I did what you said and got 10392.3 for Lmin. However the program I am using is telling me it's the wrong answer. Could you or someone else confirm this?

Thank you,

-M

Do you get a = 1154.7 (correct to 1 decimal place)? If not, then you've made a mistake somwhere in your arithmetic.

6. yesss!

6928.2 = Lmin

7. Fantastic,

Yes I did get that for a (1154.7).

Thanks for taking a look.