🔍 Key Concepts

• pressure conversion between inches of water and psi (pounds per square inch) • the standard relationship: about 27.7 inches of water = 1 psi • setting up a ratio or unit-conversion to go from inches of water to psi

💭 Think About

• How can you express 9 inches of water as a fraction of 27.7 inches of water, if 27.7 inches is equal to 1 psi? • Once you have that fraction, what does that number represent in psi, and which choice is closest to it? • Are any of the answer choices clearly too large to be the pressure from only 9 inches of water column?

✅ Before You Answer

• Use the approximate conversion 1 psi ≈ 27.7 in. H₂O for low pressures. • Compute 9 ÷ 27.7 (or a close mental estimate) before looking at the choices. • Verify that your result is a small decimal psi value (< 0.5 psi), since 9 inches of water is a relatively low pressure.