Having 2 glasses, in one is 10 cl of tonic and in the other 10 cl of fernet. Overspill 3 cl of tonic to the glass with fernet and after thorough mixing overspill 3 cl of the mixture back to the glass with tonic. Is it now more tonic in the glass of fernet or more fernet in the glass of tonic?
(Ignore chemical composition!)
There is exactly as much tonic in the glass of fernet as there is fernet in the glass of
tonic.