Question 1107535
Let x=the length
There are two lengths so 2x
There are 3 shorter sides, all equal.
The lengths of the shorter sides are each (160-2x)/3
The area, 1000 yd^2=x(160-2x)/3
3000=160x-2x^2
2x^2-160x+3000=0
x^2-80x+1500=0
(x-50)(x-30)=0
x= 30 yds or 50 yds

Look at 50
Each length is 50 
the width is (160-100)/3 or 20 feet for each.
This is 1000 yds^2 50*20, and is the best answer, since the shorter side is 20.

Look at 30.  
the lengths are 30 each and the width us (160-2x)/3=33.333; while the area is 1000 yds^2, the width is longer, so this doesn't work.