Answer: 56 tiles.
Step-by-step explanation:
Given : A builder needs to tile a 7 foot by 8 foot room with one-foot square tiles.
i.e. Area of a tile = 1 square foot.
Now, the area of the room is given by :-
[tex]\text{Area of room}=6\times8=56\text{ ft}^2[/tex]
Now, the number of tiles required is given by :-
[tex]n=\dfrac{\text{Area of room}}{\text{Area of one tile}}\\\\=\dfrac{56}{1}=56[/tex]
Hence, she will need 56 tiles.