Question 971355
The tougher shape to analyze is the circle with the diameter.


r, the radius.
{{{2pi*r+2r=600}}}

{{{pi*r+r=300}}}
{{{r(1+pi)=300}}}
{{{highlight_green(r=300/(pi+1))}}}-----radius for the circle.
Each run has almost then a max length of {{{600/(pi+1)=144*feet}}}, although the area might be more important.


The square shape with diagonal:
{{{4x+sqrt(2x^2)=600}}}
{{{4x+x*sqrt(2)=600}}}
{{{x(4+sqrt(2))=600}}}
{{{highlight_green(x=400/(4+sqrt(2)))}}}
As the value, {{{x=73.9}}} feet.
The diagonal for this square is a length of {{{2*x^2=2*(400/(4+sqrt(2)))}}}
or diagonal is {{{sqrt(2(73.9)^2)=73.9*2=highlight_green(147)}}} point something feet.


Which shape for the 600 foot length of material depends on single dimensional length is important or if area is important.  The circle shape, being near the value of the square's diagonal, might be better because of how the curve occurs near the ends of the diameter.


Area Circle,  {{{pi*r^2}}}
Area Square, {{{x*x}}}