Explanation
We a are required to get how wide the pool should be to ensure that all tiles are used
To do so, we will have to set up some equations
Firstly, let the required width be w
Since the border is 200 feet long
And a rectangle has four sides in which opposite sides are equal
[tex]90+90+w+w=200[/tex]Solving for w
[tex]\begin{gathered} 180+2w=200 \\ 2w=200-180 \\ 2w=20 \\ w=10\text{ feet} \end{gathered}[/tex]Therefore
The border will be 10 feet on one side and 10 feet on the other side
