jmc

There are $12$ inches in a foot, so the length of the rectangular section of floor is $36$ inches and its width is $24$ inches. It would take $36÷6=6$ tiles to cover the length of the floor and $24÷6=4$ tiles to cover the width, so a total of $6\times 4=\boxed{24}$ tiles are needed to cover the whole rectangular section of the floor.