if andrew covers the floor with square tiles that measure 18 inches on each side,how many tiles will he need, if the dimensions are 15 feet and 6 feet

15 x 6=90 square feet

1 square foot=12 x 12=144 square inches

90 x 144=12,960 square inches

But the tiles are 18 x 18=324 area of each tile in square inches

So, we have 12,960/324=40 Tiles are required.

Each tile is 1.5 ft on a side....so the total area of each is (1.5ft)² = 2.25 sq ft

And the sq footage to be covered is 15 x 6   = 90 sq ft

So

90/2.25  = 40 tiles are needed......arranged as 10 tiles by 4 tiles