To find the number of tiles required, we need to calculate the area of the floor and divide it by the area of each tile.

The area of the floor is given by: 15 m × 8 m = 120 m²

The area of each tile is given by: 50 cm × 25 cm = 1250 cm²

To convert the area of each tile to square meters, we divide by 10,000 (since there are 10,000 square centimeters in a square meter): 1250 cm² ÷ 10,000 = 0.125 m²

Now, we can calculate the number of tiles required by dividing the area of the floor by the area of each tile: 120 m² ÷ 0.125 m² = 960 tiles

Therefore, 960 tiles are required to cover the floor.

To find the fraction of the floor that is uncovered when a carpet is laid with a 1 m space between its edges and the edges of the floor, we need to calculate the area of the uncovered space and divide it by the area of the floor.

The area of the uncovered space is given by: (15 m + 2 m) × (8 m + 2 m) - 15 m × 8 m = 17 m × 10 m - 120 m² = 170 m² - 120 m² = 50 m²

Now, we can calculate the fraction of the floor that is uncovered by dividing the area of the uncovered space by the area of the floor: 50 m² ÷ 120 m² = 5/12

Therefore, the fraction of the floor that is uncovered is 5/12, which is not equal to 7/20.