step 1
The perimeter of a rectangle is equal to
P=2(L+W)
where
L is the length and W is the width
In this problem we know that
L=4W
and P=1000 ft
so
substitute in the formula of perimeter
1000=2(4W+W)
solve the equation for W
1000=2(5W)
1000=10W
W=100 ft
Find the value of L
Remember that L=4W
substitute the value of W
L=4(100)
L=400 ft
The answer is
length L=400 ft
width W=100 ft