1. Calculate the Volume - Volume of a cylinder is done by this formula, V=π*R^2*H.
3.14x1.5^2x4.5=V
V=31.79ft^3
2. Find the amount of Gallons it can hold total - V=31.79 Now per 1ft^3 its roughly 7.5 gallons. 31.79x7.5=238.44gallons
3. Find the amount occupied by the water currently in the barrel - So we need the middle point so we have something to go off of, now 2.5ft isn't half of 4.5, 2.25 is. So 238.44/2=119.22Gallons. Now 2.5 is 53.4% the difference is 3.4. So we need to take 119.22Gallons*.034=4.05 now add that to the 119.22 and you get 123.27 gallons used
4. How much is left over? - Take 238.44-123.27=115.17 more Gallons that the barrel can hold.
