Dots
A comment by Gary Corcoran:
A dotted note equals 3 notes of the next shorter value.
If we add a dot to a note its duration will increase by half its own value:
Without Dot With Dot Note Equivalence Note Equivalence
By adding an extra dot you can add half the value of the value added by the first dot. For example, if you add a double dot to a quarter note you will add an eighth (half the value of the quarter note) and a sixteenth note (half the value of the eighth note):
Translated by Carlos Soto P
English version revised by Sue Talley