Answer: The answer is (B) 400 square feet.
Step-by-step explanation: Given in the question that a swimming pool and deck are built in a rectangle with length 40 ft and width 18 feet. The pool itself is 320 square feet. We are to find out the area of the deck.
The area of the rectangle in which the pool and deck are built is given by
[tex]A_r=40\times 18=720~\textup{square feet}.[/tex]
The area of the pool is given by
[tex]A_p=320~\textup{square feet}.[/tex]
Therefore, the area of the deck will be
[tex]A_d=A_r-A_p=720-320=400~\textup{square feet}.[/tex]
Thus, the correct option is (B) 400 square feet.
