QA.
Assuming the dimensions have to be in exact feet then you could have
9ft *9ft = 81square feet
10 ft * 10 ft = 100 square feet
11 ft * 11 ft = 121 square feet.
QB.
If each tile is 1 ft * 1 ft ie 1 square foot
Then
9' * 9' would mean 125 - 81 = 44 tiles would not be used
10' * 10' = 125 - 100 = 25 tiles not used
11' * 11' = 125 - 121 = 4 tiles not used
