Answer: (H) 1215.
Step-by-step explanation:
To cover a 9' x 9' floor, we need (9 x 12) = 108 inches of flooring in each direction.
Each 1' x 1' tile covers an area of (12 x 12) = 144 square inches. Therefore, we need (108 x 108) / 144 = 81 tiles.
Each 3" x 3" tile covers an area of (3 x 3) = 9 square inches. Therefore, we need (108 x 108) / 9 = 12,096 tiles.
The difference in the number of tiles needed is: 12,096 - 81 = 12,015.
Therefore, we need 12,015 more 3" x 3" tiles than 1' x 1' tiles.