60 square feet = 60*12*12 = sq inches.
Therefore, minimum number of tiles required = 60*12*12/(18*18) = 26.66...
ie 27 tiles.
That is the classroom answer to the mathematical question. However, in real life, the area to be covered may not be of a shape in which whole tiles can be used. In that case, unless you can use all the offcuts you will require more tiles.
You'll need 200 18-inch tiles.
266.666666666 so rounding up 267 tiles.
It is not clear what is meant by an "18x18 square feet" tile. 18ft * 18 ft = 324 square feet, so that one tile will be more than enough. An 18 inch by 18 inch tile cannot be a 18x18 square feet tile.
2.25 square feet
5,184 2-square-inch tiles are needed.
220
You'll need 200 18-inch tiles.
22.2 tiles so buy 23 tiles.
266.666666666 so rounding up 267 tiles.
It is not clear what is meant by an "18x18 square feet" tile. 18ft * 18 ft = 324 square feet, so that one tile will be more than enough. An 18 inch by 18 inch tile cannot be a 18x18 square feet tile.
18" x 18" = 1.5' x 1.5' = 2.25 square feet90/2.25 = 40 tiles.
2.25 square feet
It depends on the units used for measuring the tiles. Obviously, the number of 18 inch x 18 inch tiles required will not be the same as 18 cm x 18 cm tiles. And if there were 18 yard x 18 yard tiles, you would need only 1.
5,184 2-square-inch tiles are needed.
144/(1.5*1.5) = 64 tiles, but if you are using this to determine how many are needed to tile a room, you need to add at least 10% for edging around the room. So, you probably need at least 71 or more tiles.
225 16-inch tiles.
875 24-inch tiles.