[tex] \green{ \boxed{\sf \: length \: \: = 70 \: \: feet}}[/tex]
Step-by-step explanation:
Let assume that,
So,
Given,
perimeter = 200 feet
We know that,
Perimeter = 2(length + wide)
So,
[tex]200 = 2(x + 40 + x) \\ = > \frac{200}{2} = 2x + 40 \\ = > 2x + 40 = 100 \\ = > 2x = 100 - 40 = 60 \\ = > x = \frac{60}{2} \\ = > x = 30 \: feet[/tex]
So length = x + 40 = 30 + 40 = 70 feet