Erin is buying floor tile to put in a room that is 10 ft. by 15 ft. She has chosen tiles that are 18 in by 18 in. Assuming that she needs to buy 10% extra to be safe, how many tiles will she need to buy?

18 inches first of all is 1.5 feet, since 12 inches is 1 feet, and 6 inches is 0.5 feet

so lets see what area we need. 10 ft by 15 ft = 150 ft^2

now out tile area is 1.5ft by 1.5 ft = 2.25 ft^2

150/2.25 = 200/3=66+2/3, we need atleast 66 and 2/3rd of a tile, we must by atleast 10% to be extra safe so

10% of 66+2/3 is 6.6 + 2/30, so we will by 66+2/3 + 6.6+2/30 = 73.3333333333, so we will by a total of 73 tiles.