A rectangular room measures 8 m by 6 m. It is to be tiled with square tiles of side 40 cm. How many tiles are needed to cover the floor completely?

Convert room dimensions to cm: 800 cm × 600 cm. Area of room = 800 × 600 = 480,000 cm². Area of one tile = 40 × 40 = 1,600 cm². Number of tiles = 480,000 ÷ 1,600 = 300. Option B results from failing to convert metres to centimetres, while option C arises from using 20 cm instead of 40 cm as the tile side, and option D from a unit conversion error on only one dimension.