The answer will depend on the measurement units used for 3x6.
270
It depends on how big the tiles are.
Tiles that are two feet on a side cover 4 square feet. 378 of them cover 1512 square feet.
76.6 tiles
67 tiles.
192 tiles
start with 38 tiles.
157 18 by 18 tiles are needed to cover 352 square feet.
0.25 sqare feet= 1 feet.
4,036 sqare miles (mi^2)
616 3x6 inch tiles are needed to cover exactly 77 square feet.
Two tiles will suffice since they will cover 36 square feet.