Hello, Ron!
A swimming pool is 25 ft wide, 60 ft long, 3 ft deep at the shallow end, and 15 ft at its deepest point.
If the pool is being filled at a rate of 800 ft³/min, at what rate is the water level rising
when the depth at the deepest point is 5ft?
Side view of the pool . . . Ignore the top 3 feet. Code:
: - - - - 60 - - - - - :
- *-----------------------*
: | x *
: - +---------------*
12 : |:::::::::::*
: y |:::::::*
: : |:::*
- - *
The area of the water is: . 
From similar right triangles, we have: . 
The area of the water is: . (y)\:=\:\frac{5}{2}y^2)
The volume of the water is: . 
Differentiate with respect to time: . 
We are given:
ft³/min and 
So we have: . \cdot\frac{dy}{dt})
Therefore: .
ft/min.