Acylindrical pressure vessel has a height of 9 feet and a diameter of 6 feet. how much gas can the pressure vessel hold when full?

Height of the cylindrical pressure vessel = 9 feet
Diameter of the cylindrical pressure vessel = 6 feet
Then
Radius of the cylindrical pressure vessel = (6/2) feet
                                                                   = 3 feet
Then
Volume of the cylindrical pressure vessel = πr^2h
                                                                   = 3.14 * (3)^2 * 9 cubic feet
                                                                   = 3.14 * 9 * 9 cubic feet
                                                                   = 254.34 cubic feet
So the amount of gas that the cylindrical pressure vessel can hold is 254.34 cubic feet. I hope the procedure is clear enough for you to understand.