Answer
Here the area and the width of the rectangular fence are given. We have to find length of the fence.
( diagram )
The area A of a rectangle is given by the formula A=lw where l is the length and w is the width.
Given that area is 500 square feet and width is 20 feet.
Substituting values in formula,
⇒500=l×20
⇒20/500
= 20/1×20
[ Dividing both sides by 20 ]
⇒l=25 feet
∴ length of rectangular fence is 25 feet.
Hence, the answer is 25.