## College Physics (4th Edition)

The correct answer is: (a) $20~cm~Hg$
$P_{abs} = P_g+P_{atm}$ The absolute pressure of the gas is $20~cm~Hg+76~cm~Hg$. The gauge pressure is the difference between the absolute pressure and the atmospheric pressure. Therefore, the gauge pressure is $20~cm~Hg$ The correct answer is: (a) $20~cm~Hg$