Answer:
400
Explanation:
Enough that you will need a large piggy bank to take money out of.\
There are 4 squares of equal size that will fit the floor of a 20 by 20 foot room.
Therefore you will need 4 * 100 = 400 tiles.
You could do it by noting that the floor has 20 by 20 tiles which is 20^2 which is 400.