Question

A pressure gauge connected to a tank reads 380 kPa while the barometer reads 745 mm Hg. What is the absolute pressure in the tank?

Answer 1

The pressure gauge is used to measure the difference between the tank pressure and surrounding atmosphere pressure: $p_G=p_T-p_A.$

745 mmHg is 99325 Pa. Therefore, the absolute pressure in the tank is

$$p_T=p_G+p_A=479325\text{ Pa}.$$