About 17.
192 tiles
1296 Tiles
616 3x6 inch tiles are needed to cover exactly 77 square feet.
157 18 by 18 tiles are needed to cover 352 square feet.
500/1.78 = 281 tiles
118
10
Each tile covers 4 square feet. You will need 24.75 tiles to cover the area.
If the tiles are 1 foot squares, it will take 1,650 of them to cover 1,650 square feet. If the tiles are 16 inch square (1-1/3 square feet, each), then it would take 1,238 tiles.
It will require a minimum of 1,462 tiles. That number will cover about 1,850.34 square feet.
20
480