Answer:
66 gallons
Step-by-step explanation:
Given that initially 160 gallons of a solution containing 12% salt.
So, the initial amount of salt = 12% of 160 = 12/100 x 160 = 19.2 gallons.
Let x gallons of water get evaporated so that the remaining solution contains 20% salt.
The remaining amount of solution = 160-x gallons.
As the initial amount of salt is still in the solution which is equal to 20% of the remaining solution, so
19.2 = 20% of (160-x)

gallons
Hence, 66 gallons of water must be evaporated to get a 20% salt solution.
Volume of a cylinder is given by V = πr^2h
Since the content of the storage tank completely filled the 25 identical cylinders, this means that the volume of the 25 cylinders combined is equal to the volume of the storage tank.
25(πr^2h) = 235,500
πr^2h = 235,500/25 = 9,420
h = 9,420/(3.14 x 5^2) = 9,420/78.5 = 120.
Therefore, the height of the cylinderical containers is 120 in