1. **Problem statement:** A vacuum gauge reads 5.4 psi and the barometric pressure is 28.5 in Hg. We need to find the absolute pressure in the tank. 2. **Formula:** Absolute pressure $P_{abs}$ is related to gauge pressure $P_{gauge}$ and atmospheric pressure $P_{atm}$ by: $$P_{abs} = P_{atm} - P_{gauge}$$ Note: Vacuum gauge pressure is subtracted from atmospheric pressure because it measures pressure below atmospheric. 3. **Convert barometric pressure from inches of mercury to psi:** Given 1 in Hg = 0.491154 psi, $$P_{atm} = 28.5 \times 0.491154 = 13.998 psi$$ 4. **Calculate absolute pressure:** $$P_{abs} = 13.998 - 5.4 = 8.598 psi$$ 5. **Interpretation:** The absolute pressure in the tank is approximately 8.6 psi, which is the actual pressure relative to a perfect vacuum. This method uses the relationship between gauge, atmospheric, and absolute pressures and unit conversion for barometric pressure.