The given coordinates are (1, 5), (6, 5), (6, 1) and (1, 1). Draw a rectangular figure using these coordinates.
The measurements of each side are 4, 4 ,5, and 5. Therefore the perimeter of the patio is:
4 + 4 + 5 + 5 = 16 feet
If each grid of the square is 3 feet. The measurement of the upper part of the patio is 5 + 3 + 3 = 11 feet. The other side is 3 + 3 + 4 = 10 feet. So the total area of the patio plus the bricks is 10 x 11 = 110 sq. feet. The area of the patio is 4 x 5 = 20 ft.
Therefore, the remaining area is 110 - 20 = 90 ft.
