GCAP Operator 2 Practice Exam 2026 – Complete Prep Guide

To find the humidity ratio, which is typically expressed in grains of moisture per pound of dry air, it's important to use the relationship between dry bulb temperature, relative humidity, and the saturation point of air at that temperature.

At a dry bulb temperature of 100°F, the saturation vapor pressure can be determined, which corresponds to the maximum amount of moisture the air can hold at that temperature. Using tables or calculations based on psychrometric principles, you can find the saturation vapor pressure for 100°F is around 0.9 inches of mercury (or equivalent in other units).

With a relative humidity of 60%, you can calculate the actual vapor pressure by multiplying the saturation vapor pressure by the relative humidity expressed as a decimal (0.60). The actual quantity of moisture in the air can then be calculated based on this vapor pressure.

When these values are plugged into the formula that relates the humidity ratio, moisture content in grains can be derived. The result you reach after calculating all these values points to 176 grains as the amount of moisture in the air given these initial conditions.

Thus, the humidity ratio of 176 grains makes it clear that at a dry bulb temperature of 100°F and relative humidity of 60%, the air holds significant