🔍 Key Concepts
• Use the dry-bulb temperature (78°F) along the bottom axis and the wet-bulb temperature (68°F) using the sloping wet‑bulb lines on the chart.
• Locate the intersection point of the 78°F dry-bulb and 68°F wet-bulb lines, then follow the nearest curved/diagonal relative humidity line that passes through that point.
• Remember that a larger difference between dry‑bulb and wet‑bulb temperatures means lower relative humidity, and a smaller difference means higher humidity.
💭 Think About
• What dry‑bulb scale value on the bottom corresponds to 78°F, and where does the 68°F wet‑bulb line cross above it?
• Once you find that intersection, which labeled relative humidity curve (10%, 20%, 30%, etc.) is closest to or passes directly through that point?
• Given that the dry‑bulb and wet‑bulb differ by 10°F, should you expect the humidity to be very low, moderate, or very high? How does that help you narrow down the answer choices?
✅ Before You Answer
• Confirm you are using 78°F on the bottom axis (not 26°C) for the dry-bulb location.
• Verify you are following the correct sloping line for 68°F wet-bulb, not a nearby value like 70°F or 65°F.
• Before choosing, double-check that the humidity curve you read at the intersection matches one of the listed percentages in the answer choices.