V/Q = 1 is an approximately value.. even the MORE correct version of V/Q = 0.8 itself is approximate provided that certain conditions are met such as cardiac output, breathing frequency etc.
To specifically answer your question:
Ventilation of the lung is 4L per minute and Perfusion of the lung is 5L per minute - both being
approximate because obviously each breath you are taking as you are reading this sentence is not gonna be the same rite. So, the approximate number comes from 4/5 = 0.8
To go beyond your question:
The
significance of the ratio is what we should be most concerned about and especially for step1 purposes. Even inside our lung, the ratio is different and im going to assume that you have grasped the concept why apex of the lung would have higher V/Q value and a lower value at the base. Then you have to apply this to pathological states and also be able to connect this to Pa O2 and Pa CO2 values. And of course have some understaning of A-a values connected to this. Keep working hard
