If the partial pressure of water vapour at 27°C is 18 mm Hg and the saturated vapour pressure of the atmosphere at the same temperature is 24 mm Hg, the relative humidity at this temperature is?

A. 25%
B. 33%
C. 75%
D. 82%

Correct Answer:

Option C – 75%

Explanation

Relative Humidity = (S.V.P. of water at dew point)/S.V.P of water at air temperature =(18)/24 x 100% = 75%