#### Answer

The dimensions are $6\times12\times30$

#### Work Step by Step

We know that the side lengths are $6, x,$ and $2.5x$. The formula for the volume of a rectangular prism is $lwh$. So, our equation is $6\times x\times2.5x=2160$, which equals $15x^2=2160$. Then, we divide both sides by 15 to isolate $x^2$ to get $x^2=144$. Take the square root of both sides to get $x=\pm12$. The answer is 12 because the length of a pool can't be negative.
Now, we substitute 12 into $x$ and $2.5x$, which were the dimensions that we determined in the beginning.
$x=12$
$2.5(12)=30$