Answer :
a).
The 8" by 7" tile covers 49 square inches.
The 21" by 21" tile covers 441 square inches.
b).
The area of the floor is (420" x 630") = 264,600 square inches.
c).
It would take (264,600) / (441) = 600 large tiles to cover the floor.
d).
Emmanuel should use the big tiles to cover his floor.
-- A big tile costs 4 times as much as a small tile, but it has 9 times
as much area as a little tile has, so it is a better buy.
-- Plus, he would have to pay the floorman a lot more to glue down 5,400 tiles
than he will have to pay to glue down only 600 tiles.
-- Since he has hired my services to advise him, I will charge him only 15%
of the difference if he takes my advice, so he will still be money ahead.
The 8" by 7" tile covers 49 square inches.
The 21" by 21" tile covers 441 square inches.
b).
The area of the floor is (420" x 630") = 264,600 square inches.
c).
It would take (264,600) / (441) = 600 large tiles to cover the floor.
d).
Emmanuel should use the big tiles to cover his floor.
-- A big tile costs 4 times as much as a small tile, but it has 9 times
as much area as a little tile has, so it is a better buy.
-- Plus, he would have to pay the floorman a lot more to glue down 5,400 tiles
than he will have to pay to glue down only 600 tiles.
-- Since he has hired my services to advise him, I will charge him only 15%
of the difference if he takes my advice, so he will still be money ahead.