If you have a value for the actual water vapour pressure in the atmosphere and and estimate for the saturation vapour pressure you can compute relative humidity by using Eq (1).

RH (%) = (e / es)

100

Eq (1)

Where e is the actual vapour pressure and es is the saturation vapour pressure. The saturation vapour pressure is dependent on Ta If you are given a dew point temperature (Td) reading, the actual vapour pressure can be determined by using the saturation vapour pressure chart below.

Use the above information and your knowledge of RH and Ty to answer the question that appears below the chart.