To solve this problem we first need to calculate the volume of the tank at full capacity, since it is a cylinder we can use the appropriate formula shown below:
volume = pi*r²*h
Where r is half the diameter. Since the diameter of this tank is 1.5 feet longer than the height and the height is 9.5 feet, then the diameter is equal to 11 feet, so the radius must be r = 11/2 = 5.5 feet. We can now use the formula:
volume = pi*(5.5)²*9.5 = 902.815 feet³
Since someone consumed 1/7 of the water, the remainder must be 6/7 of the total volume. So we have:
remainder volume = (6/7)*volume = (6/7)*902.815 = 773.841 feet³