Answer:
640
Explanation:
The area of the bathroom is 40 square feet.
Think about how many 3 inch tiles you need to make 1 square foot: you would need to line up 4 3-inch tiles to be 12 inches long, times 4 3-inch tiles to be 12 inches wide.
So each square foot will take 4 x 4 tiles, or 16 tiles.
There are 40 square feet, each with 16 little tiles.
40 x 16 = 640 little tiles.