The width of the field is 2.5 feet.
The formula for the perimeter is 2 (length) + 2 (width). Since we know the length and perimeter, we can substitute and solve.
2 (505) + 2 (width) = 1015
1010 + 2 (width) = 1015
1010-1010 + 2 (width) = 1015 - 1010
2 (width) = 5
width = 2.5 feet
That means that the width of the field is 2.5 feet.