We know that we need 100 tiles for a 10 ft by 10 ft room.
We have to calculate how much we will need for a 50 ft by 50 ft room.
We have at least ways to find this values.
One of the ways is to find the area covered per tile, and then calculate the number of tiles needed for a 50 x 50 ft room.
The other is taking into account the scale of the sides: when we increase the side length from 10 ft to 50 ft, the scale factor for each dimension is 5.
Then, the area will increase by a factor of 5² = 25.
Then, we will need 25 times the tiles we used for a 10 x 10 ft room.
Then, the number of tiles needed is:

We can use the first method to check the answer.
The 10x10 ft room has an area of 10*10 = 100 ft². If we need 100 tiles for this floor, each tile covers one square foot.
We can now calculate the area of the 50x50 ft floor:

Then, if each tile covers one square foot, we will need 2500 tiles.
Answer: 2500 tiles.