S = 7 + 13 + 19 + 25 + ....... + 601
→ stabilesc cati termeni are suma cu ratia = 6 ( 13 - 7 = 6; 19 - 13 = 6,...... )
( 601 - 7 ) : 6 + 1 = 594 : 6 + 1 = 99 + 1 = 100 termeni are suma
→ aplic formula lui Gauss
S = 100 × ( 7 + 601 ) : 2
S = 50 × 608
S = 30 400
