Perimeter = 2(L+W)
Area = L * W
1 yard = 3 foot
This implies that the length is (30 * 3) 90 feet longer than the width
Therefore L = W + 90
So Perimeter = 2(W+90 + W) = 600 = 4W + 180
Therefore W = 420/4 = 105
L = 105 + 90 = 195
Area = 195 * 105 = 20,475 Square feet
Hence the Maximum area of the field the chalk could outline is 20,475 Square feet