Answer:
![V = 25d ^ 3 + 275d ^ 2 + 250d](https://img.qammunity.org/2020/formulas/mathematics/middle-school/gm6u034s7o9lk5cvkw7bqyod0pmz6nbvk9.png)
Explanation:
If the pool has a rectangular shape then its volume can be written as:
V = Width * Length * Depth
Let's call:
w = width
l = length
d = depth.
So we know from the statement of the problem that:
![d = d](https://img.qammunity.org/2020/formulas/mathematics/middle-school/aiml3913r3swnz8l65x02m4uhm49j8b1ye.png)
(5 feet more than 5 times the depth)
(50 feet more than 5 times the depth)
Then, the volume can be written according to the depth as:
![V = d(5 + 5d)(50 + 5d)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/sxynkoheu3lntlluwmosfpwnr0i7q6yntt.png)
![V = d[250 + 25d + 250d + 25d ^ 2]](https://img.qammunity.org/2020/formulas/mathematics/middle-school/xzr1drwmuq274fffofqnj3ytmuvmepx8uw.png)
![V = 25d ^ 3 + 275d ^ 2 + 250d](https://img.qammunity.org/2020/formulas/mathematics/middle-school/gm6u034s7o9lk5cvkw7bqyod0pmz6nbvk9.png)