How many tiles, each 50 cm * 50 cm, would be needed to cover a floor 5 metres 4 metres? What would be the cost of these tiles if I had to pay £7.50 for 10 tiles?

50 cm in meters is 0.5 m

Area covered by a tile = 0.5 * 0.5 = 0.25 m^2

Total area for floor = 5 * 4 = 20 m^2

Tiles required = 20/0.25 = 80 tiles

If 10 tiles cost £7.50 then 1 tile = £7.50/10

then 80 tiles = 7.50/10 * 80 = £60.00