Answer:
[tex]D=13.8\ ft[/tex]
Step-by-step explanation:
we know that
If the tank half-filled with water is at 20 feet, then the height of the tank is 40 feet
The volume of the cylindrical tank is equal to
[tex]V=\pi r^{2}h[/tex]
we have
[tex]h=40\ ft[/tex]
[tex]V=6,000\ ft^{3}[/tex]
assume
[tex]\pi =3.14[/tex]
substitute and solve for r
[tex]6,000=(3.14)r^{2}(40)[/tex]
[tex]r^{2}=6,000/[(3.14)(40)][/tex]
[tex]r=6.9\ ft[/tex]
Find the diameter
Remember that the diameter is two times the radius
[tex]D=6.9*2=13.8\ ft[/tex]