Hey there!!
If we read the question, we get to know, the volume of the tank = 11,000 ft³ and the shape is spherical.
The volume of a sphere = ( 4/3 ) ( πr³ )
We know the volume and now we just get this into an equation.
11000 = ( 4/3 ) ( πr³ )
Divide by 4/3 on both sides
... ( 11000 ) / ( 4/3 ) = πr³
... 11000 × 3/4 = πr³
... 8250 = πr³
Remember - π = 22/7
... 8250 = πr³
Divide by π on both sides
... 8250 / 22/7 = r³
... 8250 × 7 / 22 = r³
... 2625 = r³
Cube root on both sides
... ∛2625 = r
... r = 13.7 ft
Diameter = 2 × radius
Diameter = 2 × 13.7
... 27.4 ft = Diameter
Hope my answer helps!!