Final answer:
To cover a 90cm by 120cm floor with 9cm by 4cm tiles, 300 tiles are needed. Calculate the area of the floor and one tile, then divide the floor area by the tile area.
Step-by-step explanation:
To find the number of tiles needed to cover the floor of a room that is 90cm by 120cm, with each tile measuring 9cm by 4cm, first calculate the area of the floor and the area of one tile. The area of the floor is 90cm x 120cm, which equals 10,800cm². The area of one tile is 9cm x 4cm, which equals 36cm².
Next, divide the total area of the floor by the area of one tile to find the number of tiles needed:
Number of tiles = Area of floor / Area of one tile
Number of tiles = 10,800cm² / 36cm²
Number of tiles = 300
Therefore, 300 tiles are needed to cover the floor.