Question

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

Answer 1

Right.

Answer 2

The amount of gas that will fill the cylinder when full is exactly equal to the volume of the cylinder.
That is:
\[V _{c}=\Pi*r ^{2}*h=\Pi*(\frac{ 6 }{ 2 })^{2}*9=81pi\]
Hence, that amount is 81 pi or 81*3.14 feet cube of gas that can fully fill the cylinder.