The room is a square that is 21 feet by 21 feet.
Therefore, there are 441 square feet. You will need enough tile to cover 441 square feet.
The square room is 21 x 21 feet, equaling 441 square feet. The number of tile needed will differ based on the size of the tile. To find the number of tile needed, simply, divide 441 by the square footage of each tile. For example, if each tile is 2 X 2 (4 square feet), then divide 441 by 4. In this case it would take 110.25 or 111 tiles.
The room is 21 feet by 21 feet and that means the room is 441 ft squared. The amount of tiles needed depends on the size of the tile. To find the amount of tiles needed, all you have to do is
441 square feet/ the size (in square feet, of course)
the room is 21 by 21 so just multiply those 2 numbers
`21xx21=441` so you will need 441 tile if the tile is `1xx1`