Răspuns :
sirul e : 3, 6, 9, 12, 15, 18, 21, 24, 27, 30
nr pare sunt : 6, 12, 18, 24, 30 => exista 5 numere pare in sir
nr pare sunt : 6, 12, 18, 24, 30 => exista 5 numere pare in sir