Question

Square tiles 9-inches on a side cover the floor of a rectangular room exactly. the border tiles are white and all other tiles are blue. the room measures 18 feet by 15 feet. how many tiles are white

Answer 1

first convert feet to inches:
18 ft × (12in/1ft)= 216 in
15 ft × (12 in/1ft)= 180 in

divide each side of the room by 9 inches to get number of white tiles per a wall

wall 1(18ft): 216in/9in= 24 white tiles
wall 2(15ft): 180in/9in= 20 white tiles
wall 3(18ft): 216in/9in= 24 white tiles
wall 4(15ft): 180in/9in= 20 white tiles


Lastly, add up all the white tiles and subtract 4 (the tiles that we counted twice because they were the corner tiles and touched both walls)

24+20+24+20-4= 84 white tiles total