Looking at this chart:
. . . it is not hard to see the perfect fourths (remembering always that a perfect fourth is made of two whole steps plus a half step).
DO to FA
. . . is a P4
MI to LA
. . . is a P4
RE to SOL
. . . is a P4
DO to MI would
NOT
be a P4
MI to SOL would
NOT
be a P4
FA to TI would
NOT
be a P4
(Watch out for this one!)
