Verified answer

Psig (pound-force per square inch gauge) is a unit of pressure relative to atmospheric pressure at sea level. By contrast, psia measures pressure relative to a vacuum (such as that in space).

55 psig + 15 = 70 psia (rounded)

15 psi is the approximate atmoshheric pressure, which is normally taken as 14.7 psi .

Hello, yes you are undoubtedly correct, Pabs=Pgauge+Patm 1 atmosphere= 14.Sixty nine psi so 10 atm = 146.9 psi abs = 132.21 psig just consider that strain is consistently expressed as a difference between two points. A average strain gauge shows a pressure between some measured point and atmospheric pressure. An absolute strain gauge indicates a stress difference between some point and nil strain. I'm hoping this helps!

The first one. You need to keep the units the same, all psi

Also the air pressure will add to the gauge pressure, so you add 15, not subtract