Question

The management of a large store wishes to add a fenced in rectangular storage yard of 20000 ft^2 using the building as one side of the yard. Find the minimum amount of fencing that must be used to enclose the remaining 3 sides of the yard.

Answer 1

Okay, I am confused on what formula to use

Answer 2

Called away a short time ago.

area = h*w, 20000= h*w
perimeter = 2h + w

Solve 20000 = h*w for w and plug the result into the RHS of the perimeter equation.
Take the derivative of the resulting RHS, set the derivative expression to zero and solve for h.

Answer 3

Thank you!

Answer 4

You're welcome and thank you for the medal.

If you have access to the Mathematica 8 program, then this problem could have been solved using the Constrained Optimization function, Minimize:
\[\text{Minimize}[\{2h+w,w h==20000,w>0,h>0\},\{w,h\}] \]\[\{400,\{w\to 200,h\to 100\}\} \] The 400 is the minimum perimeter value.

No knowledge of the Calculus required with this approach.

Answer 5

Oh, okay, thanks I didn't know about that! Thank you !