What is the weight of air in a room 16.5 ft long, 7.5 ft wide, and 8 ft high, if 10 ft3 of air weighs 27 lb?

First, determine the volume of the room by multiplying its dimensions such that,

                 Volume = Length x Width x Height

Substituting,
 
                volume = (16.5 ft)(7.5 ft)(8 ft) 
                  volume = 990 ft³

To determine the mass, we multiply the obtained volume by the density.

                mass = (990 ft³)(27 lb/ 10 ft³) 
                       mass = 2673 lb

2673 lb