🔍 Key Concepts

• Use the intersection of the dry bulb (bottom scale) and wet bulb (slanted lines from the left) on the psychrometric/dew point chart • From that intersection, follow the horizontal line to the right-hand scale labeled dew point (°F) • Notice how small changes in the intersection point (because wet bulb is 66.5°F, not 66°F or 67°F) affect the dew point reading between grid lines

💭 Think About

• First, locate 78°F on the dry bulb (bottom) axis and trace straight up until you meet the slanted line for about 66.5°F wet bulb—where should that be between the 66°F and 67°F lines? • From that exact intersection, if you move horizontally to the right, what dew point value does it line up with on the right-hand scale, and which answer choice is closest to that value? • Compare the dry‑bulb/wet‑bulb spread (78 − 66.5) with the spreads for nearby points on the chart—does a larger spread usually give a higher or lower dew point?

✅ Before You Answer

• Be sure you’re reading the wet bulb value from the sloping lines, not the vertical or horizontal ones • Confirm that you follow a perfectly horizontal line from the intersection to the dew point scale at the right margin • Check which two labeled dew point grid lines your point falls between, then see which answer choice is numerically closest to that position