How are the partial pressures of 3 gases A,B and C related to the total gas pressure?

Answer 1

The partial pressure of gas A divided by the total pressure, gives you the mole fraction of the gas in the mixture.

The same calculation can be done for the other gases.

And the partial pressures of A + B + C = Total Pressure

(all assuming that the mixture contains ONLY A, B, and C)

Answer 2

The partial pressure of a gaz is the pressure calculated as if the gaz fill all the volume possible

If pA, pB and pC are the partial pressure of the three gases , total pressure is

P = pA+pB +pC