Please refer to the following document:
https://dl.dropbox.com/u/63664351/MATS2005/1N%20-%20Engineering%20Units%20and%20Pressure%20in%20Statics%20Fluids.pdf

Page 8.
PV=RT/M. But since n=m/M , shouldn't PV=mRT/M?

Question:
On a certain day the barometric pressure at sea level is 30.1in.Hg, and the temperature is 70°F. The pressure gage in an airplane in flight indicates a pressure of 10.6psia, and the temperature gage shows the air temperature to be 46°F. Estimate as accurately as possible the altitude of the airplane above sea level.

Question

Please refer to the following document:
https://dl.dropbox.com/u/63664351/MATS2005/1N%20-%20Engineering%20Units%20and%20Pressure%20in%20Statics%20Fluids.pdf

Page 8. 
PV=RT/M. But since n=m/M , shouldn't PV=mRT/M?

Question:
On a certain day the barometric pressure at sea level is 30.1in.Hg, and the temperature is 70°F. The pressure gage in an airplane in flight indicates a pressure of 10.6psia, and the temperature gage shows the air temperature to be 46°F. Estimate as accurately as possible the altitude of the airplane above sea level.

anonymous · Answer

the author has used the symbol "V" for "volume per unit mass" and not "total volume"

The height can be calculated using barometric formula for non uniform temperature of the atmosphere. However we are not given the temperature gradient as such but we can take it to be (T2-T1)/h where h is the height of the plane.