The least amount of fabric needed to cover the cushion is 22 square feet.
Step-by-step explanation:
The dimensions of the cushion is
  1 x 2 x 3
Let us consider,
  L = 1
  B = 2
  W = 3
The fabric covers the outer surface of the cushion. So we need to find the surface area of the cushion.
The surface area is calculated by
  Surface area = the area of 6 sides of the cushion
  Surface area= 2( lb + bw + wl)
            = 2{( 1x2)+ (2 x 3) +( 3 x 1) }
            = 2{(2)+ (6)+ (3) }
            = 2{11}
            = 22 square feet
The least amount of fabric needed to cover the cushion is 22 square feet.
